some questions about the underlying implementation principle of gdb

Hello:
     I am an undergraduate, and i am studying gdb. I have some questions
about the underlying implementation principle of gdb.
     I learned that the implementation of gdb is related to ptrace.
Therefore，how does gdb debug programs through ptrace?  More specifically, I
recently learned the awatch command，ignore command(ignore n number (n is
watchpoint number))，continue command. how does gdb implement the
commands（awatch ignore continue）？
   Thank you!