Why would I want to put information on my web page that is not visible to the typical viewer?

I would want to put information on my web page that is not visible to the typical viewer because the information might affect the web page itself. Sometimes the information is not be meant to be seen by a viewer but helps your web page run smoothly and is needed in order for the web page to have all the correct code. Metadata is a type of invisible code in the head that is needed in your webpage for it to run smoothly.