Does anybody know what plant is this?
This tree looks like a Ficus Benjamina or close relative. These are also common office and house plants because they are fairly easy to care for. They tolerate low light levels fairly well, though they may not support as many leaves when the light is so low.
In humid conditions they sometimes grow air roots out of their branches. If the roots touch the ground, they develop into secondary truncks.
You just have to keep them watered properly. Which is to say, loose well draining soil but watered often enough that the soil never gets dry.