Acne is when a pore of the skin gets filled with something, and the body swells up around it. A Blackhead is when that "something" is dark dirt and pus, so that the acne pimple looks like a bubble with a dark central core.
Blackheads are a very normal type of acne. The should not be "popped" or touched in any way, because the act of opening up the bubble could cause infection and make things far worse - even leaving a scar. Follow the other suggestions on this site in order to remove the Blackheads and to prevent them from returning.