We have Straight Talk, and you can get either GSM (ATT carrier) or CDMA (Verizon) phones, depending on where you live and which carrier is in your area. At least that's how it works here. The phones may vary depending on which carrier you choose.
If you don't have a smartphone, you can get a $30 per month card which will give you 1500 minutes, unlimited texts, and 100MB data. I believe all the smartphones require the $45 per month cards, which I think is the unlimited plan.
We live in sort of a dead area, so our coverage at the house is "iffy" at times. However, in town there is no problem and even our little flip phone works great.
We rarely use the phone, but I keep it for emergencies.