You have seen Se used as a reflexive pronoun in Spanish, but it also has some other uses:

1. As the impersonal subject ‘you,’ ‘one,’ ‘people’: Se come bien en este restaurante (‘One eats well in this restaurant’); ¿Cómo se dice ‘today’ en español? (‘How does one say today in Spanish?’); Nunca se sabe (‘One never knows’). Notice that in this construction, the verb is always in the third person singular.

2. In passive constructions: Aquí se habla español (‘Spanish is spoken here’); Se venden libros (‘Books are sold’). Notice that in these constructions the verb may be in the third person singular or plural, depending on whether the thing you’re referring to (the grammatical subject) is singular or plural.

Note that the formal command of dar, dé, loses the accent mark when a single pronoun is added to form the affirmative command: Deme el libro (‘Give me the book’).