Why does mould grow on food?

Mould grows on food because the food is certainly gone bad. Letting the people know that's its gone bad it grows mould and also mould grows because that food may have been lying somewhere for a long time also mould grows when it lies in 1 place after a while there is no space left for the air so then the juice from that certain product goes all over the place in a certain time becoming mould. Shabirah