The web client is connected to the internet when needed. It basically always runs a web browser software. It uses HTTP and requests web pages from the server and receives web pages and files from the server. The Web Server is always continually connected to the internet. It runs web server software and alike the Web Client, also uses HTTP. It receives a request for a web page, responds and transmits the status codem web page, and whatever files are associated with it.
Two protocols used on the internet to convey info that use the internet but not the web are the Transmission Control Protocol (TCP) and the Internet Protocol (IP.)
Similarities between the URL and a domain name are that in the URL, it describes different chunks and what they mean. An example being that it has HTTP Protocol, it shows the subdomain or Web Server Name, Domain Name, Folder Namem, and Web Page File Name. This is similar to the Domain because the Domain describes or identifies parts that are related to specific things like Top-Level Domain Names. Differences are that the URL is describing the entire every part of every precise location the web page or whatever you are looking at has. The Domain Name just has certain logical names for web pages.