Schemas are repeated play behaviours. The one I talk about in my training all the time is:
"A five year old child picks up a handbag from the home corner. They put it on and walk around all day. As they walk around they pick up various items from around the room. A numicon plate here, a piece of playdough there, maybe even a bit of sand. By the end of the session the bag is full of treasures. The bell goes and off the child goes. The handbag is returned to the home corner and you find it at 5:30pm on your way out. Who gets to empty it?" haha - you do!
This is transporting and filling schema in action. They're perfectly natural and normal. Some children display them, some don't. Some adults display them, some don't.
Now I could go into incredible depth here but I'm a firm believer of not reinventing the wheel so rather than me explain all the bits to go with schema there are some links below to some absolute top notch guides.
Other wonderful guides + places to go: