Verbs can be versatile and the action they express can even change the way we construct our sentences. Verbs are actually the bosses of any sentence. In fact, the only part of a sentence that is absolutely necessary is the verb. They are so powerful that they can have a bunch of other sentence parts working for them.
1. There are verbs that don't need any person involved in the action:
2. Some other verbs need an agent, someone to perform the action:
3. There are verbs that don't work unless they have an agentandan object:
(Yo) tengo dos hijos.
I have two children.
4. Lastly, there are verbs that need an agent, an object and a recipient.
(Yo) Me envié un email a mí.
(Yo) Te envié un email a ti.
(Yo) Le envié un email a ella/él.
(Yo) Nos envié un email a nosotros.
(Yo) Os envié un email a vosotros. 🇪🇸
(Yo) Les envié un email a ustedes/a ellos.
The two parts marked in red refer to the same person, the recipient. Literally, we say: "I sent you an email to you" te envío un email a ti. We use the second part ("to you") only if we want to emphasize who is the recipient.
For you, the most important thing to remember are these pronouns, which by the way, are used for indirect objects or recipients.
Other verbs look like this:
enviar algo a alguien → send something to someone
dar algo a alguien → give something to someone
comprar algo a alguien → buy something for someone
regalar algo a alguien → give something (as a present) to someone