Debian is an operating system, based on the Linux Kernel, that allows users to customize their experience through the interface and the applications that are available.
In terms of the interface, Debian allows users to change how they interact with the operating system through components known as desktop environments. These include, but are not limited to, GNOME, Xfce, and KDE Plasma. Through these sets of programs, users are able to change the visual elements on their computer and which applications they start off with.
However, aside from the programs that come with one's chosen desktop environment, Debian also works with many open source applications. For instance, there are programs such as Krita that allow users to draw images on their computer. Furthermore, there are collections of applications such as the Libreoffice suite. This assortment of programs allows users to write documents, create presentations, and even make spreadsheets. Overall, similar to other operating systems, Debian's limitations are pushed through the availability of multiple applications that users can work with.
In summary, Debian is an operating system that allows users to choose how they want to interact with their computer, through the customization of their desktop environment and selection of applications.