It's a phrase that implies something unexpected or unusual is taking place. It can also be used to ask if something is wrong or if there's a problem.
Here are some examples of how "pasa algo" can be used:
* "¿Pasa algo?" (Is something happening?)
* "Parece que pasa algo" (It seems like something is going on)
* "No creo que pase algo" (I don't think anything is wrong)
Let me know if you have any other Spanish phrases you'd like to understand!