What do expressions even do?

[AntDX316]

Alt+Left-Clicking the wick icon makes it show an expression. If you just Left-Click is it the same?

[Dan Ebberts]

Not sure what you mean by the wick icon, but you can create a default expression by alt+clicking a property's animation stop watch icon. If you just click that icon it will create at keyframe at the current time (or remove all keyframes if one or more already exist).

[MarekMularczyk]

Expressions allow you to extend what After Effects can do.

For example, I use expressions to create animated infographics where some values (like percentages for some statistics) animate from 0 to a specific value. You can't do that by hand, without expression. It would drive you crazy 😉

[AntDX316]

show a small demo

[MarekMularczyk]

Alt+click on stopwatch icon next to a property adds an expression.

Just click on stopwatch icon adds just a keyframe.

That's the difference.

[AntDX316]

so they are the same?

[RobShultz]

Alt clicking gets you into an expression menu where you can link properties together or write code.

Left clicking is different. Left clicking mainly adds or removes keyframes.

[AntDX316]

What if you get into the expression menu but right no code, can you still operate like it's keyframe only mode?