Imagine our economic system were like a large number of buildings filled with electrical outlets(jobs). Some of them full, some of them empty. Imagine we all had a tail with plugs at the end. The plugs(skills) can fit into the electrical sockets. Now our task is to figure out a socket that would fit our plug the best. For some people they can simply plug in with no modification. For others, they need to chisel off their plugs to fit it in somewhere. Now some outlets provide higher electricity(money). Some people use step up transformers(education) to pull out more current. It is necessary to sign a contract (employment terms) for using the outlets where we can plug for 9hours everyday. Certain other outlets can be used with part-time contracts (half time) but provide much lower current.