The Staff is a medical research station, later designed to house pregnant women who were taken there to give birth and/or die. It consists of a long corridor, at the end of which is an operating room, as well as a nursery and a locker room. Hidden inside one of the lockers is a switch that unlocks a hidden vault that contains medical equipment and nursery furniture. There is also another hidden room, where the Others take women who have become pregnant on the Island to die.
Just warning you, that if you haven't watched the whole show might see some information before you are ready. To help with that we have this nifty filter. Just set it to the episode you you are upto, and we'll do our best not to spoil anything.