Whats up with the Twinkles? (Mexico City)

Hey, so maybe this is a rather stupid question.... but whats up with the Twinkles? I don´t understand how they work... should one answer a twinkle? or twinkle back? is being twinkled a good or a bad thing? is it internations equivalent to the Facebook poke? and if so, now that we are on the matter can someone please help me understand that feature as well hahaha
Sorry but technology is playing games with my mind

Saludos!
Lucia