Telogen Effluvium is Telogen Effluvium, which is a very sudden and traumatic loss of hair. It can be brought on by a number of things, but generally is induced by some sort of very dramatic hormonal 'shock' to your system, so to speak. Pregnancy, for example, has been known to cause Telogen Effluvium in women. Stress-induced breakdown can also cause it.
Telogen Effluvium is rare, and is distinguishable from male pattern baldness in that male pattern baldness is hairloss in a pattern, whereas Telogen Effluvium is generalized.
Thus, if you are losing hair, and your hairloss or hair thinning is in the stereotypical 'norwood' pattern, then chances are you have male 'pattern' baldness, hence the name.
Many people wishfully think that their hairloss is Telogen Effluvium, as hairloss from Telogen Effluvium is inevitably grown back, whereas male pattern baldness is not.