This chapter is an attempt to unlock some of the elegance and logic behind the After Effects Timeline, which is not always evident to the new user. Shortcuts and other workflow enhancements are designed to help streamline what might otherwise be tedious or exacting edits.
If the information seems overwhelming on first read, remember that most of it is tied to specific contexts. You don't need to memorize every shortcut or tip, but if you keep the working scenarios in mind, you can refer back to related advice as needed.
Selections The Key to Compositing