The first word is actually 'Korar', not 'Karar'
Both means 'of DOING', 'to DO', 'for DOING' etc. depending on the context.
1. Koribar- is a formal way of saying it. However, please keep in mind that it is not used in conversations. It is used/seen mostly in books, like The Bible, newspapers etc where the context is presented to us in an honorable manner.
2. Korar- is the colloquial way of saying it. It can be used in both conversations and in books.
I hope things are clear now. If you have any more questions, please ask...^_^