What is Expression 2?

can someone briefly explain to me what it is?

Something related to wire, and from then on I have no idea.

ok, but can anyone just explain whhat it is/what it can do?

With expression 2 you get a text box in-game where you can code. The language used is a made up language created using Lua. After you write your code you left click to spawn the Chip. Expression 2 is capable of doing anything gates can, and more.
As I said, you can write your own code with it, which makes it much more powerful than regular gates. You can for example create something very complex with just a few line of code instead of 30 wire Gates.

you can do all of your multiplication division subtraction and addition in one chip instead of many single ones. And it’s not just limited to that. You can put forces on entities, work with vectors, create holograms, and improve the efficiency of contraptions by an extreme amount.

It will also process faster than chips.