Actors are instances of classes that derive from the AActor class;
Objects are instances of classes that inherit from the UObject class;
UObject:the base class of all objects in Unreal Engine, including Actors.
Actors can be thought of as whole items or entities, while Objects are more specialized parts.
gameplay classes such as GameMode, GameState, and PlayerState set the rules of the game
A Pawn is an Actor that can be an “agent” within the world.
A Character is a humanoid-style Pawn.
A Controller is an Actor that is responsible for directing a Pawn.
A HUD is a “heads-up display”, or the 2D on-screen display that is common in many games.
The PlayerCameraManager is the “eyeball” for a player and manages how it behaves.
GameMode is the definition of the game, including things like the game rules and win conditions. It only exists on the server.
GameState contains the state of the game, which could include things like the list of connected players, the score
Unreal Motion Graphics (UMG)
UMG = lots of widgets Unreal Motion Graphics UI Designer (UMG) is a visual UI authoring tool which can be used to create UI elements such as in-game HUDs, menus or other interface related graphics you wish to present to your users. At the core of UMG are Widgets, which are a series of pre-made functions that can be used to construct your interface (things like buttons, checkboxes, sliders, progress bars, etc.). These Widgets are edited in a specialized Widget Blueprint, which uses two tabs for construction: the Designer tab allows for the visual layout of the interface and basic functions while the Graph tab provides the functionality behind the Widgets used.