You will often read that a particular star or planet "culminates" at a certain time and date. This relates to its position in your sky. As you look toward the southern horizon, objects describe an arc as they move through the sky, rising from an easterly direction and setting to the west.

The point at which the object is exactly due south is also when it's at the highest point it can reach in the sky for your latitude. That is when the object is said to culminate. Obviously, culmination is reached a little earlier each night. This is more important when it involves an object that never rises very high above the horizon -- culmination tells us in a general way when it will be best placed for observation.