A person's employability is anything that makes them able to get and keep a job. If nurses are in high demand, a nursing college might rightfully brag about the employability of its graduates.
Employability comes from employ, or "hire for a job," and its Latin root, implicare, which means "to be connected with." Your employability is your ability to be employed, or to have paid work. In general, college graduates are thought of as having better employability, but it depends what kind of job they're trying to get. If you want to work as an electrician, your training and experience matter a lot more than your education, when it comes to employability!