This page explains terms commonly used in Unreal Engine . If you have wondered “What is an Actor ?” or “What is a Component ?”, this page answers those questions and more.

After learning a term, explore the related topics at the end of its section.

Project #

The Unreal Engine 5 project contains all the game's content in folders on disk, such as Blueprintsand Materials. Organize project folders as needed. The Content Browser in Unreal Editor shows the same directory structure as the Projectfolder on disk.

Each project has an associated .uprojectfile. The .uprojectfile is used to create, open, or save a project. You can create multiple projects and work on them in parallel.

For more information, see Projects and Templates .

Blueprint #

The Blueprint Visual Scripting system provides complete gameplay scripting through a node-based interface in Unreal Editor. Like other scripting languages, it defines object-oriented classes or objects. In UE4, objects defined this way are commonly called “Blueprints.”

For more information, see Blueprints Visual Scripting .

Object #

Objects are Unreal Engine's fundamental class, acting as building blocks with basic asset functionality. Almost everything in Unreal Engine inherits from an Object.

In C++, UObjectis the base class for Objects. It provides garbage collection, metadata ( UProperty), exposing variables in Unreal Editor, and serialization for loading and saving.

For more information, see:

• Unreal Architecture

Class #

A Class defines the behavior and properties of an Actor or Object. Classes form a hierarchy, inheriting information from parents and passing it to children. Create them in C++ or Blueprints.

For more information, see:

• Blueprint Class

• Gameplay Classes

• Page not found

Actor #

An Actor is an object placed in a level, such as a camera, Static Mesh, or Player Start. Actors support translation, rotation, and scaling and can be spawned or destroyed through C++ or Blueprint gameplay code.

In C++, AActoris the base class for Actors.

For more information, see:

• Actors

• Actors and Geometry

Casting #

Casting attempts to treat an Actor of one class as another class. It can succeed or fail; success gives access to functionality specific to the target class.

For example, a game may have different volumes affecting a player. One is Fire , which reduces health over time. When the player overlaps any volume, cast that volume to Fire to access its damage-player-health functionality.

• If the cast succeeds, the player is standing in fire and begins losing health.

• If it fails, the player is in another type of volume and health is unaffected.

Casting differs from checking class membership. A check returns yes or no, but does not let you interact with class-specific functionality.

For more information, see:

• Casting in Blueprints

Component #

A Component is functionality added to an Actor.

An Actor can use the functionality its Components provide. For example:

• A Spot Light Component makes it emit a spotlight.

• A Rotating Movement Component makes it rotate.

• An Audio Component lets it play sounds.

Components must attach to an Actor and cannot exist independently.

For more information, see:

• Components

• Components Window

• Components

Pawn #

Pawns are an Actor subclass representing an in-game avatar. A player or game AI can control a Pawn, including as a non-player character (NPC).

A Pawn controlled by a human or AI is possessed . Without either controller, it is unpossessed .

For more information, see:

• Pawns

• Possessing Pawns

Character Character #

Character is a Pawn subclass intended for player characters. It includes collision setup, bipedal-movement input bindings, and additional player-movement code.

For more information, see:

• Characters

• Setting Up a Character

• Setting Up Character Movement

Player Controller #

A Player Controller turns player input into game interactions. Every game has at least one and it commonly possesses a Pawn or Character to represent the player.

Player Controllers are also primary multiplayer network-interaction points. The server has one per player to make network function calls. Each client has only its own Player Controller and uses it to communicate with the server.

The associated C++ class is PlayerController.

For more information, see Player Controllers .

AI Controller #

Like a Player Controller possessing a player's Pawn, an AI Controller possesses a Pawn representing an NPC. Pawns and Characters receive a basic AI Controller by default unless possessed by a Player Controller or configured not to create one.

The associated C++ class is AIController.

For more information, see AI Controllers .

Player State #

The state of the player represents a participant, such as a human or a bot simulating one. Non-player world AI does not have Player State.

Player State may contain:

• Name

• Current level

• Health

• Score

• Whether the player holds the flag in Capture the Flag.

In multiplayer, all Player States exist on all machines and replicate server data to clients for synchronization. This differs from Player Controller, which exists only on the represented player's machine.

The associated C++ class is PlayerState.

For more information, see Gameplay Framework Quick Reference .

Game Mode #

The Game Mode defines the rules of play, including:

• How players join.

• Whether the game can be paused.

• Game-specific behavior such as victory conditions.

Set the default Game Mode in Project Settings and override it for individual levels. There can be only one Game Mode per level.

In multiplayer, Game Mode exists only on the server and the rules are replicated, or sent, to connected clients.

The associated C++ class is GameMode.

For more information, see:

• Game Modes .

• Setting Up a Game Mode

Game State #

The state of the game is a container of information to replicate to every client: the game state for everyone connected.

Game State may contain:

• Match-score information.

• Whether the match has started.

• How many AI characters to spawn based on player count.

In multiplayer, each player's machine has one local Game State instance, updated from the server's Game State.

The associated C++ class is GameState.

For more information, see Game State .

Brush #

A Brush is an Actor describing a 3D shape, such as a cube or sphere. Use Binary Space Partition (BSP) Brushes to define level geometry, for example when quickly blocking out a level.

For more information, see:

• Geometry Brush Actors

• Content Examples

Volume #

Volumes are bounded 3D spaces whose purposes depend on their effects. For example:

• Blocking Volumes are invisible and stop Actors passing through.

• Pain-Causing Volumes damage overlapping Actors over time.

• Trigger Volumes are programmed to fire events when Actors enter or leave.

For more information, see Volume Actors Reference .

Level #

A Level is the play area you define, containing everything the player sees or interacts with, such as geometry, Pawns, and Actors.

Unreal Engine saves each level as a separate .umapfile, which is why levels are also called maps .

For more information, see:

• Levels

• Level Editor

World #

A World contains the game's levels and handles level streaming and spawning dynamic Actors.

For more information, see:

• World Settings

• Level Streaming

Source: https://docs.unrealengine.com/5.0/en-US/unreal-engine-terminology/