Shares represent the proportion of your LP tokens in relation to the total amount of LP tokens in the vault. When a new vault is added, 1 share = 1 LP. But as rewards compound, 1 share becomes greater than 1 LP. So your amount of shares will not change over time, but their value in LP will. (LP tokens stands for Liquidity Provider tokens)
The amount of shares you have is important to know for when you want to withdraw from a vault, since this is the amount you enter is in shares.
To make it easier to know the amount of LP or AVAX you will receive upon withdrawing, please refer to the text below the box.