Okay kiddo, so you know how sometimes you go to a physical bank with your parents to put your allowance money in your savings account? Well, a direct bank is a type of bank where people can do all of their banking online and don't have a physical location to go to.
You can think of it like buying things from an online store instead of going to a physical store. When you want to put money in your account or take money out, you can do it all on your computer or phone instead of going to a bank building.
Direct banks are usually able to offer better deals on things like savings accounts and credit cards because they don't have to pay for a physical building and can save money that way. It's like when you buy things online and they cost less because the company doesn't have to pay for a store building.
So that's what a direct bank is, it's a bank that you can use online and doesn't have a physical location for you to go to.