i think of the image of a rabbit crossing a street at night, frozen in the glare of on-rushing headlights :) There is a bewildering, rapidly evolving/changing, range of methods to create websites that can be developed through programming; that can be hosted in a browser; that go beyond the original web toolkit of HTML, CSS, simple JavaScript.
Web Applications, Web Components, TypeScript driven apps via ASP, Blazor, Angular, Uno, Ionic, React, JavaScript+libraries, Java based frameworks, server-side based tools like Node.js: you might say it's a race where all the participants are "handicapped" by the fact that the browser must end up with HTML and, optionally, CSS.
All addressing security and rendering to different OS's, browsers, and screen sizes in different ways.
I have Googled, watched videos, asked friends, I just don't get it.
i think your research will start yielding "chunks you can digest." If you research these strategies separately: there is no shortage of excellent overviews and tutorials for each of them ... but, they are often changing in ays you must attention to use (like Angular whose latest version often breaks the previous version.
Pick one or two of the "frameworks" that use a language/OS/IDE you are familiar with, and explore those in more depth.