you know how some friends you make, you make for life. you know them inside out. you finish each other's sentences. you might as well have been twins.
there are others who become your friends for a period of time, when you share something in common. and afterwards, depending on how much effort you put in, you might remain good friends or mere acquaintances saying hi and bye whilst you hurry by hoping s/he wouldn't stop you for a chat.
and then there are those you thought you knew, but you don't. not at all. not even close. one day you are playing in each other's paddling pool probably half naked, and the next you realise that that person you came to love and know so well is someone completely different. and you share nothing in common anymore. and it withers into nothingness.