(Source: Ferenc Husvéth)
Capacitation, generally speaking, is the change sperm undergo in the female reproductive tract that enables them to penetrate and fertilize an egg.
This step is a biochemical event; the sperm moves normally and looks mature prior to capacitation. It is important to note that once the sperm reaches the egg, it does not mean that it is capable of fertilizing it immediately. In order to fertilize the egg, the sperm must undergo the process of capacitation in the reproductive tract where a number of enzymes and signaling molecules are involved. This process can take around 10 hours, which means that the fertilization time is approximately 24 hours.