What is the TL;DR of the category? What do tools in this category let you do?
Web development tools are for writing websites and web applications. They include tools that run on the 'back-end', or server, that handle requests for data/files coming from the 'front-end', or client, which is usually a web browser.
Why would I need to use it? Why would I need to start using it?
One would use these tools if they want to write websites or web applications. Start using these if you want to host something on the Internet or tie an application to the web.
Where in the application design/pipeline is this category of tools used? Learn more.
This category spans all tools in web development. These tools are more than just web servers and clients.