* Cómo se llama: This is the formal way to ask "What is your name?" You use it for someone you don't know well, someone older than you, or someone in a position of authority. It's similar to saying "Mr. Smith, what is your name?" in English, even though we know it's a bit redundant!
* Cómo te llamas: This is the informal and casual way to ask "What is your name?" You use it with friends, family, people you're comfortable with, and generally people your age or younger. It's like saying "Hey, what's your name?" in English.
Here's a handy way to remember:
* Se is used in more formal situations.
* Te is used in more informal situations.
Let me know if you have any other questions about Spanish grammar!