There are different definitions of price. Perhaps the simplest definition is to say "price is the value of a product (good) or service". A price is expressed in other goods, services, or in money.
Here is an example about price: Peter raises sheep for their wool. Sally raises chickens for their eggs. Winter is coming, so Sally wants to make a warm wool coat. She first measures how much wool she needs for a coat. She thinks she needs the wool from 2 sheep for the coat. She then goes to Peter and asks him what he wants for the wool she needs. Peter then tells her the price he is asking for his wool. Sally might trade some of her chicken eggs for the wool.
Sometimes trading eggs for wool is difficult. So people invented something they called money. This is cash or currency used for trading.
If Peter does not need eggs, he will not trade his wool for eggs. The price for his wool in eggs is zero, but Peter does need something else. So Sally goes to a market and sells some of her eggs for money. Then she goes to Peter and gives him money for the wool. How much money Peter wants for his wool is the price.