A more thorough explanation:

A teller's check is a type of check that is drawn by a bank on another bank or payable at or through a bank.

For example, if you need to make a large payment and don't want to carry cash, you can go to your bank and request a teller's check. The bank will then draw the check on their own account and give it to you to give to the recipient.

Teller's checks are often used for large transactions because they are considered more secure than personal checks. Since the bank is the one issuing the check, the recipient can be sure that the funds are available and that the check will not bounce.