The low post in basketball is a location on the court where players position themselves. It is located just near the basket just above one of either of the low blocks. There is also a location on the court called the high post, which is on the edge of the free throw line.
Since the low post is in very close proximity to the basket, it can be a vital part of the court for a team's offense. Typically, the center or power forward will 'post up' by putting his or her back to the basket as they position themself on the low block. They will then call for the ball, pivot to face the basket, and shoot either a short jump or hook shot, layup, or attempt a dunk.
It can be very difficult to defend a dominant low post player, but it is absolutely crucial to a team's success. The best way to defend the post is to deny the post player the ball by playing close, vigilant defense. If they do receive the ball, deny them any easy shots by putting your hands in the air and preventing them from taking any space.