It's a casual and informal way to get someone's attention, similar to "Hey" in English. It can also be used to tell someone to listen to what you're about to say.
Here are some examples of how "oye" can be used:
* Oye, ¿cómo estás? (Hey, how are you?)
* Oye, ¡mira esto! (Hey, look at this!)
* Oye, ¿puedes ayudarme con esto? (Listen, can you help me with this?)
* Oye, ¡deja de hacer eso! (Hey, stop doing that!)