Let's start here: we're nerds. We like to do nerdy things and have fun with it. Thus, we've "nerded up" our career paths.
Career paths at ESS are defined five ways: archetypes, classes, specializations, talent trees, and levels.
Archetypes are broken down into classes
Classes are broken down into specializations
Specializations have talent trees
Spending points in talent trees is real-world training at Elegant Software Solutions
Your level is a combination of years of experience and projects worked.
The class or classes you choose, what you specialize in, how deep you go into the talent trees, your level, and your performance reviews are all combined to determine your salary.
If you're a geek like us, you get what we just said. If you're not, just go with it; this part probably doesn't apply to you anyway.