The numbers are the generation they are. So 2 is last year and 3 is what came out this year basically. First generation do not have a number on them. There’s also different colors that will make them a certain addition. Like a gray addition etc. They usually cost more as well. There’s no real way to visually tell the difference in the 2nd ad 3rd generation because they usually have similar color concepts. If read the description it will say things like now the battery lasts longer than before (12 hours instead of 8), but they do come with chargers and can be charged with an android charger as well. If they are charged for 5 minutes it adds 2 hours of playback time so really just depends on what you want to spend. Hope helps!