Hip Hop is a culture. It's a style. It's how you talk, it's how you dress, and it's how you live daily.
Let's not forget the elements though. Hip Hop consists of four distinct elements/pillars:
1. The DJ. Recongized as the backbone of hip hop, the DJ or turntablist provides the music and therefore controls the mood of his audience. A good DJ should be able to get a feel for his listeners and provide what they want to hear. If they want to dance, he needs to play dance-able music. If they want to chill, he should play something more mellow. As has been said, Kool DJ Herc was the first to extend the break of the record by playing two of the same record and switching back and forth between them. The DJ is the main ingredient of hip hop, and everyone else is his arms and legs.
2. The MC or emcee. Short for Master of Ceremonies, the MC calls the crowd and gets them pumped. He might spit a rhyme or two, but originally MC-ing wasn't about rapping. Rap came later and almost killed hip hop. The MC is really about speaking verbally for the DJ, or making announcements.
3. The B-Boy. A b-boy is a breakdancer. In fact the term "b-boy" is short for "break-boy." But here, "break" didn't come from breaks on the record, but rather street terminology. If you were "breaking" at a party, you were causing trouble or acting crazy. It also referred to the status of the people living in the Bronx. You could say, "He broke. He went through a breaking point." So the exaggeration was applied to the dance at the time.
4. Graffiti. Graffiti is wild style art. It usually takes the form of spraypaint on the sides of buildings or boxcars, which is illegal. But graff is still art, which sparks many debates between pro-graff and anti-graff groups. Some don't consider graffiti an element of hip hop, and this holds true with low quality tags, but in general it fits with hip hop very well.
Hip Hop lives and breathes. It is a way of life and a state of mind. The beauty of Hip Hop is that it is a positve reaction from people living in a negative environment (the ghettos/projects). How can that not be respected, if not embraced by society?