The World Wide Web popularly called the Web or WWW is an information system made up of resources and users on the internet using protocols like HTTP (hypertext transfer protocol).
Invented by Tim Berners-Lee in the year 1989 who wrote the first web browser in 1990 while at CERN.
The web is one of the primary medium people used to interact on the internet. Some media on the web such as web pages are presented in the HTML (Hypertext Markup Language).
To access a resource on the web you literally need the resource address which is either an IP address or a domain name.
IP Address can be numeric strings separated by dots (.) e.g.
192.168.2.1 for IPv4 addresses or digits separated by columns for IPv6 e.g
2031:0db8:85a3:0000:0000:8a1e:0370:7304. You can read a short guide on IPv4 and IPv6 available at Mashable.
An IP Address is used to locate resources on the web by typing it into the address bar of your web browser but most (except for a few) are not comfortable typing numbers all the time just to look up a resource online. Which brings us to the domain name.
The domain name is a more of a human-friendly version of an IP address, and it's quite easy to memorize (huh, not all the time).
Beginner's guide to a domain name can be found on wpbeginner.
History is quite a big thing, and when it comes to the web it's almost the same. I will not be doing justice to this topic if I just write one or two lines and call it a day. But, we are in luck! Someone already did the grunt work for us. His name is Jay Hoffman. Jay Hoffman has a project dedicated entirely to the history of the web you can find at thehistoryoftheweb.
You can also read the timeline of events.
Follow his writing on the site's blog.
Edited September 19, 2020: Grammar fix.
Edited March 23, 2021: Grammar fix.