“Graffiti” stickers - what do they mean?

This is probably going to show how lame I am but I see these stickers all over public poles and signs - someone is having these custom made and mostly they seem like gibberish.

For example, stopped at a traffic crossing this morning, someone has stuck a sticker that said “BOTHER HEAL JAER”. Is it a band? Slam poetry? Just a tag??

Do these signify anything to anyone? Is there some meaning I’m missing?

I don’t necessarily mean just this particular sticker - I’ll try to get some pictures of other stickers I see around….