The interface

The editor window has a top bar, the hierarchy on the left, the inspector on the right, the viewport in the middle with three tabs under it, and a status bar along the bottom. Drag a panel's tab to move it, or drop it on another panel to share its space. View > Reset Layout puts everything back.

The editor with the player selected

New here? A first look at the editor goes through the areas one by one with a numbered picture.

The areas

AreaWhat it is forPage
Top barThe menus and the play controls, with preferences and export on the rightTop bar and menus
ViewportThe scene, to look round and arrange things inViewport
HierarchyEvery entity in the scene, as a treeHierarchy
InspectorWhat is selected, to change itInspector
AssetsThe project's filesAssets
ConsoleWhat the engine and your scripts loggedConsole and history
HistoryEvery change, to go back toConsole and history

Every built-in component, and what each of its fields does, is in Components.

Status bar

Along the bottom. On the left, a dot and whether the scene is Saved, has Unsaved changes, is Playing or is Paused, then the scene's file and how many entities it has. On the right, how many entities are selected, the frame rate, how long the editor's last frames took on the CPU and the GPU, and the version. The frame figures can be switched off in Preferences.

Unsaved changes

Switching project, opening another scene and quitting ask first when the scene has unsaved changes. The question lists the changes that would be lost, newest last, and offers Don't save, Cancel and Save.

The unsaved changes question, listing what would be lost

Keys that work everywhere

KeyDoes
Ctrl+SSave the scene
Ctrl+Z, Ctrl+Shift+ZUndo and redo
F5, F6Play and stop, pause and go on
FBring the selection into view
F3The Performance window
Ctrl+,Preferences

On macOS use Cmd for Ctrl. Shortcuts lists them all.