Welcome to Android Central! They're usually for different variants depending on the region (e.g. US vs Global), so they might have slightly different band support. But I can't find any information about multiple variants for that phone -- can you show where you see that?
Hard to find any details about those variants. Variants can be specific to a certain carrier or region. It looks like the -3 version might be AT&T: www.att.com/device-support/article/wireless/KM1447373/Motorola/MotorolaXT21313. The DL variant looks like it's for MVNOs like Tracfone. Otherwise, I'm not sure what the other ones are for.