where do combinatorics play a role in computer science?

I am graduated from computer science. I need some advice in Combinatorics material related to master fields of computer science. I already know that discrete mathematics have a key role in some concepts which I need a little more elaboration. In which fields could I trace combinatorics concepts and theorems and techniques?

I am graduated from computer science. I need some advice in Combinatorics material related to master fields of computer science. I already know that discrete mathematics have a key role in some concepts which I need a little more elaboration. In which fields could I trace combinatorics concepts and theorems and techniques?