Whenever liquidity were deposited into a pool, unique tokens known as Liquidity Pool Token (LP Token) are minted and sent to the provider’s address. These tokens represent a given liquidity provider’s contribution to a pool. The proportion of the pool’s liquidity provided determines the number of liquidity tokens the provider receives. If the provider is minting a new pool, the number of liquidity tokens they will receive will equal sqrt(x * y), where x and y represent the amount of each token provided. Just imagine that the LP token is the receipt token that proven your contribution in the pool. For example, when you provide a funds into any physical project, they will give you a letter of grant ownership in order to proof that you are one of the shareholders. LP Token is exact the same with that protocol.