Learn Russian: Соседи часто приходят к нам вечером. - Neighbors often come over to our place in the evening.

The word часто (often) tells us this is a repeated, habitual action. For repeated actions, you must use the imperfective verb приходить. The perfective form (like the future tense придут) is for a one-time completed arrival.

What exactly does the prefix при- add to the verb in this sentence?

The prefix при- indicates arrival. When you attach it to the base multidirectional verb ходить (to walk/go on foot), it creates приходить, which means "to arrive" or "to come over".

Why does the sentence use к нам for "to our place"? Why not use в or на?

In Russian, when you go to a person or group of people (like "us"), you must use the preposition к followed by the Dative case (нам is the Dative of мы). Prepositions like в or на are only used when going to a place or location.

Why is "in the evening" translated as вечером instead of just вечер?