If you have watched the original Full Metal Alchemist then you have the idea how things works in FMA. But even though some stuffs works the same especially when it comes to alchemy, the story, plot and even the ending of both anime are different. They are way so different from each other.
Full Metal Alchemist: Brotherhood is the spin-off or adaptation of the original Full Metal Alchemist manga. Even though it is just an adaptation, Full Metal Alchemist: Brotherhood has better reviews, larger fan base and more likes compared to the original work of Himoru Arakawa.
The anime series ran for 64 episodes for 5 anime seasons. There are movies released and would be release soon but there will be a sixth season for FMA: Brotherhood. For me, this anime adaptation is better than the original work.