This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.
Noob - Some basic soldering is required, but it is limited to a just a few pins, basic through-hole soldering, and couple (if any) polarized components. A basic soldering iron is all you should need.
Rookie - The number of pins increases, and you will have to determine polarity of components and some of the components might be a bit trickier or close together. You might need solder wick or flux.
Competent - You will encounter surface mount components and basic SMD soldering techniques are required.
Experienced - You might be required to do some reflow or basic rework with SMD components. A heat gun, Heaterizer or other tools might be required, and a good understanding of SMD soldering as well as PTH soldering are required.
Expert - You will be required to have a firm understanding of both SMD and PTH soldering and are comfortable with rework as well. You are required to solder difficult packages like a BGA.
Want to advance your skill levels? Check out the Tutorials Section over at learn.sparkfun.com!