A bullet is a projectile. It is accelerated and released (or just fired) from a number of different weapons from a sling to a firearm. Down range, the bullet uses impact or impact and penetration to accomplish some ends. Aside from the kinetic effects (impact energy) and its ability to "enter" a target, some bullets have explosive charges within them. The word bullet can also be used in a "general" sense to refer to a cartridge or a round of ammunition. A link can be found below for more information.
You receive bullitons on Youtube when you have friends on youtube. So everytime they post something on the bulliton you will be notified. If you want to put up a bulliton press "Post a bulletion."