New to web mapping? Go through this online presentation to get a nice intro to the technology:
https://maptime.io/anatomy-of-a-web-map/ The site is down, so I forked the Maptime repo and deployed to my GitHub Pages:
https://jasonferrier.com/maptime_anatomy-of-a-web-map/
NOTE: A few pieces of this is a bit dated, but the core concepts are still how things are done.