Okay, so imagine you have two friends who live on opposite sides of a big pond. You really want them to be able to talk to each other and be friends, but they can't just swim across the pond because it's too big and deep.
So, you build a bridge across the pond. Now they can walk across the bridge and talk to each other and be friends!
A network bridge is kind of like that bridge you built. It connects two different computer networks together so that they can talk to each other and share information.
Let's say you have one computer network in your house and another computer network in your neighbor's house. You want to be able to share files and printers and stuff like that with your neighbor, but your networks are separate and can't talk to each other.
So, you set up a network bridge between your two networks. The bridge connects them together and allows them to share information and talk to each other just like your friends on opposite sides of the pond.
And that's basically what a network bridge is! It's a connection between two different computer networks so that they can talk to each other and share information.