Estoy is the conjugation of the verb estar for the first person singular in the simple present. Here the verb estar is being used as <em>location,</em> describing where I'm temporarily. On the other hand, the simple present tense is used to talk about habitual actions or routines. This tense is also used to describe things that happen now or in the near future. So <em>I am at home </em>an this is as follows:
Es lenguaje figurado porque cuando ella entra la habitacion, la habitación no se esta luminando literalmente. Es solo una forma de lenguaje figurado para mostrar que bueno se siente cuando ella llega.