How do expressions work? ( Easy explonation )

I know that it exist manual entries about expressions but i haven't been able to understand them well enough to get the hang of expressions. I have made successfull expressions but some doesn't work. I made one today that doesn't work. Expressions seem to always need " " in them. Is that rigth? Do they need ( ) too? How do you write a expressions in easy to understand words. Do you write it "( Sprite )" or "Sprite"()? I may go deeper into what my expression that doesn't work is but i just explain that if i need to.

https://www.scirra.com/manual/78/expressions

They basically express certain things in a quantitative form.

It depends on what you want to do.

Anything inside " " is just text.

Ex: "Sprite"

That is is just an expression for text with a value of Sprite.

Parenthesis () have two purposes. The first is just like in math to control what operations are done first.

Ex: 1+2*3 = 7

Ex: (1+2)*3 = 9

The second purpose is for expressions that take parameters.

Ex: sin(45)

Ex: min(1, 3, 2)

Beyond that it should be pretty simple. But feel free to post the equation you made that doesn't work and describe what you want it to do.