In Spanish we use the impersonal pronoun se with the modal verbs deber and poder to say "you must" or "you can" in order to explain general statements. The verb is conjugated in the 3rd person singular or plural, according to the direct object in the sentence.
Read and listen to these examples:
Notice the difference in the examples above with singular or uncountable nouns and plurals:
- el museo del prado / vino = se puede/se debe
- joyas / impuestos = se deben
This type of sentence is a form of passive voice which is used in Spain more frequently than the "normal" passive (ser + participle). It can also be converted into a passive sentence in English, although they may sound a bit odd sometimes, and it sounds more natural to use the form You must/You can [do something], referring to a "general you", i.e. people in general.
No se debe beber vino en exceso
Wine must not be drunk excessively (normal passive)
You must not drink excessively (general you/people)