answer:To use the AT&T data plan, you need a tablet with a SIM for 3G or 4G (meaning cellular) connectivity. It’s exactly the same feature you need if you want to use a cell phone on AT&T. A lot (most?) tablets do not have 3G or 4G. For example, if you look at iPads, they have two types – “Wi‑Fi” and “Wi‑Fi + Cellular” They all have WiFi, which you can get free lots of places with not data plan from anybody.