I am confused in the Halacha as to why it is forbidden to wear Tefillin at night as long as you dont sleep in them or desecrate them. According to Reb Meir's opinion it is Chayav B'erev v'Shabbat. Is it an Avarah to wear Tefilin at night?
Do some people wear them in the evening anyway?
please explain more
See Menachos 36a-b and Tosfos there. According to the Tana Kama, nighttime is not Z'man Tefillin, and according to the Chachamim and Rebbi Yakov it is only a Gezeirah that one not sleep in them. For a thorough discussion on the subject and on the actual Psak l'Halachah, see Sha'agas Aryeh 43-46.