Introduction
The Outliner is a list that organizes data in the blend-file, i.e. the scene data, Video Sequencer data, or anything that gets stored in a blend-file. The Outliner can be used to:
View the data in the scene.
Select and deselect objects in the scene.
Hide or show an object in the scene.
Enable or disable selection (to make an object « unselectable » in the 3D Viewport).
Enable or disable the rendering of an object.
Delete objects from the scene.
Unlink data (equivalent to pressing the X button next to the name of a data-block).
Manage collections in the scene.
Each row in the Outliner shows a data-block. You can LMB click the disclosure triangle to the left of a name to expand the current data-block and see what other data-blocks it contains. Holding Shift when clicking on the disclosure triangle will expand child data-blocks recursively. LMB Clicking and dragging along disclosure triangles will expand or collapse multiple data-blocks.