Basically an agreement (protocol) about the format to use for internet messages (requests, responses). E.g., it is agreed that HTML is a suitable response format.
In essence, a user-friendly name for a server ip address (unique identifier). In terms of the url, it is the component "abc.com" in "https://www.abc.com/shapes/rectangle".
When we travel to a house via a street address we eventually get to the "end" of the address (the house). Similarily, a URL "ends" at a function (or method) on a web server. We call this the "endpoint".
HTTP-based software architectural style with principles including statelessness, client-server (separation of concerns), and proper use of HTTP data-manipulation methods (POST/PUT, GET, PATCH, DELETE). E.g., we would not want to change data for a "GET" request.
The cachability (true/false) of data is also important.
The "representation" aspect applies to how the transferred data is represented (e.g., JSON, XML).
An imperative part of building software. Coders do "unit testing" and quality control teams apply their own test cases to the software (often the user interface).
Reusable pre-built code that typically extends a given coding language. Examples are Express (Node.js), Spring (Java) and Flask (Python). Similar to a code library.