Engineer turned entrepreneur debugging software for 15 years.
This contains some generic resources to get the basics out of the way.
One should atleast try to read the "Introduction" section of the linked wikipedia articles and not be afraid of going down the rabbit hole (reading the articles of the jargons in these articles).
Everything on the web speaks HTTP, one cannot become a web developer without a deep understanding of this protocol.
where there are browsers, there is HTML. Reading this article will only be beneficial.
The other articles that this article links to also contain a dearth of knowledge that seekers should try to go through.
Needless to say, even if you do not understand, at least read the introduction section of these articles to expand the horizon of your knowledge.