Exogen
The shedding phase. 50-100 hairs leave your scalp every day and that's NORMAL.
Grounded in the research on Hair follicle (Wikipedia) — Hair growth cycle: anagen, catagen, telogen, exogen
What exogen actually is
Exogen is the active shedding phase of the hair cycle — the moment a dead, fully-keratinized club hair detaches and exits the follicle. It runs INDEPENDENTLY of the other phases, not as a passive after-thought. The cycle: anagen (growth) -> catagen (transition) -> telogen (rest) -> exogen (release). Each follicle on your head is on its own clock, which is why you're not bald.
The real numbers
50 to 100 club hairs shed from a normal scalp every single day. At any moment ~85% of your follicles are in anagen (growing), 10-14% in telogen (resting), 1-2% in catagen (transition). Anagen lasts 2-7 years, catagen ~2-3 weeks, telogen ~3 months. Scalp hair grows about 1cm every 28 days. The 100-strands-in-the-drain panic is just exogen doing its job.