Vlad Dracula was a real person who lived in the 1400s. If you'd like know more about him try this link.
The Vlad Dracula in Buffy is based on the real person. Obviously sired sometime in the 1400s when he lived as a mortal count. He lived through the centurys, learning a lot of spells and tricks, beocming a very unique vampire. He came to Sunnydale to prey on The Slayer. Although his plan almost worked, she ultimitly defeated him.
Ok, Dracula here might throw a lot of my opinions off about the vampires in the Buffy-verse. However, I believe I can explain most of him, but keep checking back here, as I'm sure that this section will change quite often.
Anyways, Dracula in the Buffy-verse retains a lot of the original Dracula legend. However, this contradicts most of what we've seen with the vampires in Sunnydale. Dracula displayed a lot of new powers that no other vampires have had before. It is my opinion that these aren't vampire powers at all, but other magic he has learned. Dracula has learned this magic because he is a very different sort of vampire personality wise. Spike saying that Dracula's tricks were just some gypsy stuff supports this theory. Where a lot of vampires would just rather hunt and kill, he would rather dominate his victims and make them want him. Dracula also has a lot of control, which is needed to do such magic. Most vampires have nothing like as much control. This would also explain why Dracula can keep his normal human face when other vampires can't control showing off their vampire face when being attacked or feeding. Dracula's ability to survive steak hits is probably the hardest thing to explain. My only theory can be that he is able to create the allusion of being dusted so he can escape, and then live to fight another day. I have to assume Dracula was killed by some other means off camera, Buffy would not just leave him alive. He's either dead, or stuck in a jar somewhere.