The free safety in football is a defensive secondary player (FS) positioned in the defensive backfield. The free safety differs from the strong safety because free safeties stand on the weak side of the field. Both positions have similar tasks, but the role they play on defense really depends on the scheme.
In general, safeties will line up 15 yards from the line-of-scrimmage. The free safety has a job of tackling the ball carrier on both passing plays and running plays if they break through the defensive line. In a sense, they are the last line of defense. The free safety is tasked with stopping big plays before they break for an even bigger one.
While a strong safety is focused on preventing the run, a free safety is more of a pass-minded defender. This player must be able to see the entire play and make a break on the ball when it is necessary.
In order to be a successful free safety, there are several traits you must possess. For one, the free safety has to have great vision. Because they are behind the defense, they are able to see the whole play unfold. A good free safety will communicate with his defense everything that he sees on the field.
Usually the safety must be deeper than the deepest offensive player, so this means they must have a decent amount of speed. This is especially true at some of the upper levels where wide receivers are not only great at catching but also incredibly fast.
Lastly, in order to be a great free safety, one must have knowledge of various offensive schemes. They need to understand what an offense is trying to do and get the rest of the secondary in a position to prevent any positive yardage.