Guinea Pig cage help!!!!!!!!!!!!!?

Okay, I built my 2 Guinea Pigs a C&C Cage. Its a 2x4, with a 1x2 kitchen. I use fleece for the bedding. I have read and seen on Youtube videos that a lot of people use fleece for the cage, and put some type of bedding, like Carefresh, in the kitchen area. Why do they do this?? And can i do this? I used Carefresh in the entire cafe before, and still have some.