This is particularly useful on OSTree based operating systems like Fedora CoreOS and Silverblue. The intention of these systems is to discourage installation of software on the host, and instead install software as (or in) containers — they mostly don't even have package managers like DNF or YUM. This makes it difficult to set up a development environment or install tools for debugging in the usual way.
Toolbox solves this problem by providing a fully mutable container within
which one can install their favourite development and debugging tools, editors
and SDKs. For example, it's possible to do
yum install ansible without
affecting the base operating system.
However, this tool doesn't require using an OSTree based system. It works equally well on Fedora Workstation and Server, and that's a useful way to incrementally adopt containerization.
The toolbox environment is based on an OCI
image. On Fedora this is the
fedora-toolbox image. This image is used to
create a toolbox container that seamlessly integrates with the rest of the
operating system by providing access to the user's home directory, the Wayland
and X11 sockets, networking (including Avahi), removable devices (like USB
sticks), systemd journal, SSH agent, D-Bus, ulimits, /dev and the udev