Ok, basically it is an account which is held in the UK but takes payments in dollars rather than pounds. Lots of businesses and individuals have them if they regularly take payments in dollars - it saves on transfer charges and makes cheque payments easier. My former employers had one, and my business partner does. I know Barclays and Hoares do them, I am not sure about other banks. Just ask your bank if they can set one up for you, and make sure they can take cheques, and it will be just like opening another account, though obviously easier if your main account is held at the same bank.
Victoria