An escrow cushion (or reserve) is made up of funds that your loan servicer requires you to pay into your escrow account to cover unanticipated disbursements or disbursements made before your payments are available in the account. The cushion ensures that there's enough money in the account to cover possible increases in taxes or insurance. You can think of it as a buffer equal to about two months of escrow payments. (The specific amount of the cushion varies depending on state law.)
For example, if we estimate that your property taxes and homeowners insurance payments will be $6,000 per year ($500 per month); in most states we'll collect an additional $1,000 (two months of payments) for a total of $7,000. So, instead of paying $500 per month for escrow, you'd pay approximately $583 per month ($7,000 divided by 12 months).