What is the TL;DR of the category? What do tools in this category let you do?
Integrated Development Environments (IDE) take care of several aspects of code-editing. In addition to editing text, IDE's can check for errors, perform smart auto-completion on code, run tests, connect to databases, debug, and provide terminals.
Why would I need to use it? Why would I need to start using it?
One would use an IDE perhaps if a project is getting too big or if they want to have one program that handles all aspects of development. This reduces the mental overhead of switching programs and keeps the project in one place.
Where in the Programming design/pipeline is this category of tools used? Learn more.
Being in the programming/development category, IDEs don't fall anywhere in the application. They are more of a meta-category.