<3 is an ASCII heart! Its usage is varied, some examples are as followed:
- I <3 breathing
- lisa-ny <3 her fiancée
It can also be used as a retort, for example, let's say I just killed you in a game, like Ultima Online. You really got schooled. To show my disdain for you as a person I might run over to your corpse and say <3 to express my deep love for the items on your corpse.