Error: Cannot find module 'express'

'express' is a popular web framework for Node.js, and the error occurs when your code tries to import it but cannot find the module. This usually happens when the module hasn't been installed or the installation is corrupted.

The root cause is that the 'express' module is either not listed in your project's dependencies or it has not been installed in the node_modules directory. This can happen if you forget to run the installation command or if the installation failed.

To fix this error, you need to install the 'express' module using npm. Run the command 'npm install express' in your project's root directory to add it to your dependencies.