A shortage occurs when the escrow account balance at its projected lowest point for the next 12 months is below the required minimum balance, which is 2 months of payments. It helps to protect you, so you have enough funds in the account to cover an unexpected tax and/or insurance increase.
A deficiency occurs when the escrow currently has a negative balance, so funds need to be collected to reimburse the account.
If your taxes and/or insurance costs were lower than expected, your account may have a surplus. If the surplus is $50 or more, a surplus check will be sent around the same time but typically separately from your Annual Escrow Analysis. These are your funds. For surpluses less than $50, your money will be left in your escrow account.