Pre-compositions are one of the most important organizational tools in After Effects.
A precomp allows you to place several layers inside a separate composition and treat them as a single layer in your main timeline.
Imagine creating an animated title containing five text and shape layers. Instead of keeping all five layers in your main composition, you can pre-compose them into one Title Animation composition.
This keeps the main timeline cleaner and makes complex projects easier to manage.
Precomps are also useful when applying the same transformation or effect to multiple layers.
However, avoid creating unnecessary precompositions. Too many nested comps can make projects difficult to navigate.
A good rule is to use precomps when a group of layers represents one logical element, such as a title, logo, interface component or complete scene.