I saw my karma and it is 90…but I don’t have any ideia what is it… 
I don’t know if is a stupid question…but i feel curious to ask
It’s a way to indicate your activity on the answerhub, you get points for things like accepted answers and upvotes from people on your posts. So it’s similar to the post counter on most forums, but biased towards useful additions.
As an example: I upvoted this post and you now have 95 imaginary internet points / karma.