A stupid way I know is:
git diff commit-number1 commit-number2
any better way?
I mean I want to know the commit1 itself, I don't want to add the commit2 before it as a parameter.
You can see what a commit did, using git show, for that you can do:
git show <commit-id>
And to show what a commit did to stats you can use:
git show <commit-id> --stat