Twitch Subscriber Badges (Sub Badges) are badges that Twitch streamers can make available to their communities once they have reached affiliate status. Once streamers have reached the status, they can upload their own badges to their dashboard. They are then visible to all subscribers of the channel as badges in the chat next to the name.
Loyalty Badges offer your most loyal community members the opportunity to “level”. With the first subscription you get the simple 1-month badge. After 3, 6, 9 and 12 months you get an “upgraded” version. Viewers who have already subscribed to your channel at least 12 times will have a much better badge next to their name in the chat than viewers with less months. This leads to a so-called “gamification” of your subscribers. Your subscribers want to subscribe more and more to get better badges. The longer they are in your community, the greater the will to get the next bigger badge to show you and the other viewers how loyal they are to you.
If you want to upload badges for your channel, you must follow the Twitch Terms of Service:
Here you can find all other guidelines and details about Twitch Sub Badges: https://help.twitch.tv/s/article/subscriber-badge-guide?language=en_US