What is the Internal JSON-RPC error MetaMask? How to fix it?

The users who have got no idea about the Internal JSON-RPC error MetaMask should not miss out on this segment of the blog even if they have not yet faced the same error. Having some prior knowledge is not at all harmful. Who knows it might come in handy in the future. Knowledge never goes waste. And the ones who are currently facing this error should also know about what is the problem.