 Defensively, baseball players do not have any limitations on where they can stand out in the field, but they've kind of organically spread themselves into these general regions. Various situations throughout a game may call for a tweak of these positions, though. Traditional defensive alignments, which are sometimes just called defensive positioning, include playing at double play depth, where the two middle infielders play closer to second when there is a runner on first to increase the likelihood of turning a double play. The corner infielders playing closer to the lines to try to prevent a hit down the line, which will probably end up being a double, bringing the infielders up in on the grass, which usually happens if there is a runner on third base and they want to try to prevent his run from scoring, either by making it easier for them to throw him out, or just deter him from running in the first place. Or finally, in the likelihood of a sacrifice bunt, the corner infielders will come running in while the second baseman will shift around to cover first base for the throw. Over the years, and especially over the last decade, as more and more data has been collected on hitters, we have created charts that show where each ball that a player hit has landed. We call these spray charts. So if we look at a hitter's spray chart and we see that he hits the ball to the right side most of the time, it would make sense to shift our defenders toward the right side. So while double play depth is technically a defensive shift, what you'll hear on a broadcast referred to as a shift is going to be something like a second baseman playing a few feet into the outfield, or a shortstop moving to the first side of second base because that particular hitter will more likely than not hit the ball into those general areas. So if you tune into a broadcast, or even better, if you attend a game in person where this is much easier to see, and there are guys standing where you haven't seen them before, you can probably figure out what the situation is that has arisen or deducted because a hitter who is batting tends to hit the ball in one region of the field more times than not.