Tate modern - I don't get it

As you may already know I recently went on a school trip to London and one of the activities we took part in was a trip to the Tate Modern and I just didn't get the art - my favourite piece looked like it had been painted by a three year old. A rather interesting piece was a rock, some wood and some wire (how does that stuff even pass for art) so me and my mates decided that we would cerate art so far we have: paint on paper, and apple stuck to a tombstone and a piece of wood splattered with paint. I think they will sell for millions, on another note I took a picture of myself and five friends and it looks awesome like an advertisement for a film or television show, we were all on a bench and we all looked slightly odd - some were eating, I look deranged, Katie looked half asleep and Aaron didn't notice the camera at all.