The carrying capacity is the largest a population can get or the most individuals an area can possibly support. The carrying capacity is determined by limiting factors such as food, water, shelter and space. Therefore a population can continue to grow until the carrying capacity is reached.
An area of land has enough resources to support 10 giraffes. So, the carrying capacity of the area is 10 giraffes. As long as there are 10 or less giraffes in the area they will all have enough food, water, shelter and space. If another giraffe were to immigrate into the area there would not be enough food, water, shelter or space to support all of the giraffes. Some would either die or have to emmigrate out of the area.