An online check is a payment method that allows you to make a transaction using an electronic version of a paper check. This means that instead of writing out a physical check and mailing it, you can enter your bank account information and create a digital version of the check, which can then be transmitted electronically to the recipient for processing. The recipient's bank will then credit your account in the amount specified on the check, just as if they had received a paper check through the mail. Online checks are often used when making payments online or over the phone, and provide an easy and secure way to make transactions without having to physically write out a check.