Expressions are little lines of codes you put next to a property. Those lines of code create numbers or words, sometimes, that describe the behavior of a property and they do that without the need to use keyframes. There are all sorts of advantages to using expressions. Here are a few.
They let you bypass a lot of work, like video game cheat codes. You can use properties from one layer to control other layers. They use fewer or no keyframes. You can use math to describe motion. Expressions are easy to change. Finally, expressions are just text. You can find a lot of them online and simply copy them and paste them into After Effects.
Expressions can be a really helpful tool in working in projects inside After Effects. Let’s get started learning about expressions.