How come my outside AC unit is running but there's no air blowing through the vents in the house?

This is the first time I've ever had this problem. My central AC unit that's outside is running full speed, I can hear it, but my indoor air vents don't have any air blowing through them. What gives?
Update: I just removed the air filter from my inside air unit and everything inside is covered in frost/ice. What is causing this and what do I do?
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