and what do u mean by course credits
When you take a class you get a certain amount of "credit" for them. Usually, you can tell by the class number. If you're taking BIO 102:
1 - First year class
0 - I forget what it means
2 - 2 credits!
Generally, a 2 credit class would mean you go to that class for 2 hours a week, which may be multiple days or one day all at once. You need to accumulate a certain amount of credits to earn a degree. I believe it's around 100 - 150, but I think it varies based on university and major/minor.
Usually, if you earn credit(s) at another university you would want to transfer them to your current university so you don't have to take a class again. However, because every university is different on how the class is designed and some vary in credit value for that class, some credits will not be acceptable from one university to another!
For example, my sophomore year of college, I dropped out of Calculus 204 because I had a heavy course load (18 credits total). I took the class at a different university and asked my first university to transfer the credits so I didn't have to take the class again.