What do the dollar ($) and percentage (%) signs represent in x86 assembly?

Question

I am trying to understand how the assembly language works for a micro-computer architecture class, and I keep facing different syntaxes in examples:

sub $48,         


        

Answer 1

As @Necrolis said, that's written in AT&T syntax. It means:

subtract 48 from the register esp (the stack pointer).
store the contents of eax to the four bytes starting at (esp + 32).