[GreefeWrereon]

It's named "Poke" in Facebook. It's possibly some thing sweet to complete to someone to know to inform them you're only considering them (certainly not sexual or homosexual if you do it to someone of the same gender). It may be employed for teasing however. It may also be useful for just saying hi to somebody who don't actually know at all and it means they're involved in speaking more if they stick back.