Catholic marrying a Muslim??? Please help!!?

My best friend is engaged to marry her fiance who is of Algerian-Kabyle descent, but was born & raised in France. The religion he follows is Islam. They both live here in the states. I am just curious as to how do they work with there marriage with there religions & is there any differences to be made? Can she stay a Catholic & what if they have kids? She hasn't spoken of this to me. Thanks in advance for explaining it to me :)