Learn Hardcore Russian: Дружба помогает людям.

Людям is in the dative plural (отвечает на вопрос «кому?»). In Russian the verb помогать (to help) requires its object (the one who receives help) in the dative case, so you always say помогать кому? — людям.

Why is there no preposition before людям?

The verb помогать directly governs the dative case without any preposition. If you added a preposition (like к людям), it would either be redundant or change the meaning (e.g. “toward the people” rather than “help the people”).

What is the form помогает here (person, number, tense, aspect)?

Помогает is the 3rd person singular, present tense, imperfective aspect of the verb помогать. Imperfective aspect means a general or habitual action (“Friendship helps people [in general]”), not focusing on a single completed event.

What’s the difference between the imperfective помогать and the perfective помочь?

Помогать (imperfective) describes ongoing, repeated or habitual help.
Помочь (perfective) describes a single, completed act of helping.
Example:
• Дружба помогает людям (friendship helps people, generally).
• Дружба помогла людям (friendship helped people [on that occasion]).