This helps the computer to filter out all that stuff you don't want to see, just because it has a word in it somewhere that matches your search. But that is about it. You create tags, you create a style sheet to define what those tags will look like, and you can agree with others on what tags you will use in common, to define what something is. If a computer learns what a tag is, then it can search for those tags, and behave like it knows what something is really about. Instead of people having to manually run around and add links to each others pages, they can just automatically search for all related articles, far better than they can today.
Search engines work better, and people are more productive.
It is just the syntax of tags, and how they will be created. You can define the HTML language, using the XML metalanguage. Incompatible computer programs of every sort can export and import XML, and thus be able to talk to each other and share information. Preference files and settings are all being saved in XML, so that power users can read the files and alter things.