What is JSBridge

Hello
After I put the codes of the GoNativeJSBridgeLibrary file into the project and wanted to use the available methods, I ran into a problem.
The problem is that when the addCommand function is called, in the last line written JSBridge.postMessage(data)
In fact, JSBridge is not defined and it throws an error.
what is JSBridge? is it another library that I have to add or install it?

What point have I missed?

PS: My project is with NextJS