Assembly is the hard part of computing. All the good things come from this. Exploits, reverse engineering, shellcode. This is where you become 1337.
You probably have a general idea of what assembly is, but as a refresher, check this out.
Read through it up until the section on Macros.
The goal of this section is to give you an idea of what assembly is, and that it is basically just another language.
If you don't understand anything, write up what confused you so I can make the course better.