Talking about grades is all dependent on if you open up about these things or not. I know some people are very secretive about their grades, and others like me freely talk about grades. So make sure you are close friends with the person you are talking to about grades.
Grades are different depending on school. Some schools give letter grades that translates into number grade. Other schools strictly give number grades only. The difference is in letter grades, you cannot get a 3.5. You either get a B+, which is a 3.3, or an A- which is a 3.7. However, in number grades, the instructor can give a 3.4, 3.5, or 3.6.