Quasireflexive passive verbs are the ones preceded by the word se. They usually omit the person that performs the action and they are expressed in the passive form.

Let's look at some example sentences.

No se venden entradas el domingo.
Tickets are not sold on Sundays.

Los libros se compran en la librería y se piden en la biblioteca.
Books are bought in the bookstore and asked for in the library.

En la fábrica se hacen piezas de carros.
Cars' parts are manufactured in the factory.

Se alquilan teléfonos portátiles.
Portable telephones for rent.

Estas labores se realizan cuando sea necesario.
These tasks are performed whenever it is necessary.