What happens after basic training in the US military?As has been said, you go to AIT. Basic Combat Training (also called Boot Camp) is 10 weeks of training where you learn how to be a soldier - how to march, fire a gun, get fit, and survive with little sleep.
After BCT you go on to your advanced training, where you learn how to perform your job - Military Occupational Specialty (MOS). That could be infantry, cook, mechanic, radio operator, etc.
Think of it this way. Everyone in the Army needs to know how to don a gas mask, shoot an M-16, throw a grenade, etc. Not everyone needs to know how to jump out of a plane, drive a tank, fix a helicopter, or operate a satellite communications system.
BCT = what everyone needs to know to be a soldier
AIT = what individual soldiers need to know to do their specific job