I don't follow basketball much so I don't understand the home field advantage in the NBA. From what I see Celtics are the 4th seed, and Hawks are the 5th seed...so why do the Hawks have home field advantage?

In other sports this wouldn't be the case correct? At least I seem to understand the NFL's seeding and home field rules.

Also, what to do you think about their chances after what happened in game 1?