Someone please explain edexcel

So I'm transitioning from CIE to Edexcel and after looking at edexcel past papers and all that it confused me. I'm taking math, physics and chemistry. C1, C2,C3,....etc
I'm not that familiar with those. I'm an international student (if that makes a difference). And can you guys recommend good books for those subjects?
Any advice would be appreciated, thank you!