The <3 has two meanings on the streaming website Twitch.tv if used in the chat:
first is the original meaning of the heart emote, where people use it to express love towards the stream/streamer and the second meaning is used by chat bots, to remind all viewers/users on the site watching given broadcast to follow/subscribe to the streamer.
<3 emote is originally a western style emoji, it’s written left to right and rotated 90-degrees counter clockwise.
The meaning of the emote is heart (love, like) when used online or in text based conversations.
In 1993 it was turned into a red heart emoji, which became popular all over the world, hence spawning a unique addition to the original Twitch.tv emote collection in a purple variant, which comes from the colour scheme of the site.
Since its creation the heart emoji is used all around the internet and in text based mobile communication. For example, it is used daily on the most modern messenger application like Facebook messenger, WhatsApp, etc.
As of 10/12/2019 according to the website StreamElements, <3 is the 1st on the list of most popular/used emotes on the website Twitch.tv, making it the most popular emote on the site.
- Wikipedia – List of emoticons