It's the second-person formal singular present tense form of the verb "pensar" which means "to think".
Here are some examples:
* ¿Qué piensas de la película? - What do you think of the movie?
* Estoy seguro de que piensas lo mismo. - I'm sure you think the same.
* ¿Piensas ir al concierto? - Are you thinking of going to the concert?