Platicar
The verb platicar, commonly heard in Mexico, falls somewhere between discuss and chat in terms of formality.
- Bueno, tenemos mucho de qué platicar, ¿no?. We have a lot to talk/chat about. Hablar is also possible here, of course.
- ¿Ya pensaste lo que platicamos? Have you thought about what we discussed.
- Platícame, ¿cómo te va? Tell me, how are things going?
- Platícame de tu hermana. Tell me about your sister. What's her story? What's going on with her?
- Me han platicado. So I've been told. So I've heard. A rejoinder, for example, to hearing some gossip you already knew.
As you can see, you can use platicar with or without a direct object, or with a preposition phrase headed by de.
Plática
The noun plática is often a good translation for conversation.
- Estuvo muy buena la plática. We had a great chat.
- Un tema de plática. A conversation topic.
- Las pláticas prematrimoniales. Pre-marital counseling.
Chatear
Chatear exists but it is usually for instant messaging.
- Chateamos anoche. We chatted (online) last night.
Send a text message is mensajear, which is not as formal as it sounds. Textear, from the English verb text, is not yet accepted.