Se vende esta casa.
In English, you have “one,” “you,” and “they” as subjects for this type of sentence, but there's no equivalent in Spanish. The reason you have to use impersonal se constructions is precisely because these expressions lack a subject—that's why they're “impersonal.”
What is the impersonal form of SE?
The impersonal se is used when there is no clear subject performing the action, which is often the case when we make a general statement i.e. it's impersonal. For example, when we talk about general things that people do, we'll often say something like: one must, you have to, people say, they require.
How do you do SE impersonal?
The impersonal "se" is used with a third person singular verb to express the impersonal English subjects, one, you, people, or they.
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- Se abren las puertas. (The doors are opened.)
- Se vendió la computadora. (The computer was sold.)
- Se perdieron los llaves. (The keys were lost.)
- Se prohibe fumar. (Smoking is prohibited.)
