Hey Sami
The Camelot system is just a way of numbering all the keys, so you don't have to bother learning the circle of fifths.
A quick Google search will explain in detail what the circle of fifths is, but to put it simply, every major key has a relative minor key that has exactly the same notes. Every key also shares the notes that give it its colour with the key a fifth above and the key a fourth below, so mixing in either of these directions usually sounds nice. See the attached picture for examples...
Hope this helps