If you look at any of the sports lines, which are published daily in the sports page of many major newspapers, there is one team listed as the favorite, one as the underdog, and a number between them designating the official line, or expected scoring difference. In games between two closely matched teams, the line will sometimes be listed as PK or Pick. This means that neither team is a favorite, suggests the outcome is a toss-up and the betting the line involves simply picking the winner.
Often, people will confuse games listed with "no line" as similar to those listed as PK. With PK, there is a line -- of zero points given -- while a game listed as "no line" is usually an expected blowout where even the experts can't fathom a guess as to how bad the margin really will be.