Employment and unemployment
Employment and unemployment divide the labor force into two categories:
- employed people have jobs
- unemployed people are jobless, looking for jobs, and available for work
People who are neither employed nor unemployed are not in the labor force. 
- All of the progress that the US has made over the last couple of centuries has come from unemployment. It has come from figuring out how to produce more goods with fewer workers, thereby releasing labor to be more productive in other areas. It has never come about through permanent unemployment, but temporary unemployment, in the process of shifting people from one area to another.