Prepaid and pay-as-you-go cell phone services have a dirty reputation. For most of us, they conjure up images of rundown retail locations in strip malls full of smarmy salesmen, 2004-era phones, and sky-high prices to take advantage of people with poor credit.

But times have changed. Prepaid and pay-as-you-go services still offer pay-per-minute pricing for the grandpas and “emergency-only” phone owners of the world, but they’ve also started churning out some impressive unlimited monthly plans that will catch the eye of even cell phone owners who wear their contracts like wedding rings as well. Still, at $50 a month for unlimited voice and text messages, it makes you wonder: What’s the catch?

Here’s a quick-and-dirty rundown of the prepaid cell phone business, from the nitty-gritty details of how plans and providers actually work, to the pros and cons of actually buying airtime from one. Should you decide that you’re ready to chop the ball and chain and formally run into the arms of a month-to-month lover, make sure to check out our guide to the best prepaid and pay-as-you-go cell phone providers as well.