Android gives users a whole lot of customization options, some of which are useful for everyone, while others are just for power users. One of these lower level settings is the Access Point Name—better known as the APN.
The APN is something most users won’t need to worry about. You pop your SIM card into your phone, maybe reboot it, and it connects to your carrier’s network. You’ll be able to make calls, send messages, browse dank memes, and other important things. But, if you still mess around with custom ROMs, or you’re using an MVNO, you may find that things don’t work automatically.