Thoughts on creating ones own tags as I'm writing and defining content

So I’m writing and as I’m going through it, I’m writing in pseudocode, with header and paragraph tags. Then all of a sudden, I replaced a header tag with my own tag to state the definition of the words in my writing.

Example of Creation of ones own (thinking of it originally as a header <h1):

<!-- <chorus Been there and done that and going back in. end of the tags for they became invisible. Now I know... Please tell me more about that.) My thoughts before coming in to ask, I briefly looked over my XML book from Visual Quickstart, I started looking into. Then I asked myself (like I would if I had a rubberDucky) Am I in the right direction with that or do I google it? I've decided to write in here, to hear from fellow programmers who are there and know what I'm talking about. Further thoughts is that I may just see it within the Back-End with working with Databases. Am I close with that thought?

This is the idea behind JSX, Angular components, and web components. In the year 252525, web components will become standardized, but until then, you’ll have to use JS libraries to create components (“custom tags”).

Thank for the reply @PortableStick. It almost went over my head due to not being in the know with Back-End work. I’m working on that as I’m working further with JavaScript and soon intertwine it with the DOM manipulation (as I get into further focus with my current studies. I’m not there as of yet, but looking forward).