Mortgage escrow account
A mortgage escrow account is an account your lender sets up to collect extra money with each monthly payment, then uses it to pay bills like your property taxes and insurance when they come due.
New Jersey example
Say your yearly property tax bill is a made-up $10,800 and homeowners insurance is $1,800. Your lender could add $900 for taxes and $150 for insurance to your monthly principal and interest payment, so $1,050 a month goes into escrow. Lenders often collect several months of escrow payments at closing, too.
Official source
Everything You Wanted to Know About Buying a Home (NJ Department of Banking and Insurance)
This is a plain-English summary. Rules and dollar amounts change, so check the official source or a professional before you file or sign anything.