What is the TL;DR of the category? What do tools in this category let you do?
The back-end of a website or web application handles the data and the requests to access this data. Tools in this category improve this handling process, which can be in the form of performance gains, as well as the ease of writing the code.
Why would I need to use it? Why would I need to start using it?
Start using these tools when you're thinking about hosting a website or web application on a server.
Where in the Web Development design/pipeline is this category of tools used? Learn more.
These tools deal with code and the behavior of a website or web application residing on the server. Note that these tools can affect the front-end client's end result too.