"Vs." means "versus," and "versus" means "against."
It can be a legal term. Court cases are described, for example, as "James T. Brown versus the Board of Education of Topeka, Kansas." James T. Brown and the Board of Education were on two sides of the legal battle. In legal terminology, "versus" is just abbreviated "v."
It's used to describe athletic contests. "I have tickets for the Red Sox vs. the Royals."
It can be used to describe a point-by-point comparison, where two things are being compared as if they were in competition against each other. "Let's compare Windows versus Macintosh computers on speed, price, and ease of use."