What is a morning after pill?

I dont no what a morning after pill is and should I wait to see if I get my period

If you actually did this very recently I would advise getting the morning after pill immediately - NOW if possible. Any pharmacy counter has 'PLAN B' emergency contraceptive (EC) on demand - no prescription needed. EC is 85-75% effective at preventing pregnancy, and the sooner you take it the more effective it is. Any guy or gal over the age of 18 can buy Plan B. Planned Parenthood may be able to help you.
EC has a 75-85% chance of working for up to 72 hrs after the 'event' (some studies say up to 120 hrs). It is not an abortion pill. It works EXACTLY like regular BC pills, just with a stronger dose. In fact reg. BC pills can be used. ( http://ec.princeton.edu tells you how.)
Sperm will wait around for 3 days in your body waiting for an egg. EC stops the egg's release. It will not keep you 'safe' for the rest of your cycle, however.

See above, and NO DO NOT WAIT TO SEE IF YOU GET YOUR PERIOD