Anagen, catagen and telogen are terms that signify the phases of the hair growth cycle. Anagen is the phase when hair looks well nourished and grows continuosly. Right after this phase, there's a short phase known as catagen, which is a degradation period, throughout which the hair follicle is cut of from the blood supply. Throughout this phase, the hair follicle begins shrinking and the hair shaft is starting to be pushed upwards.