In order to understand the navigation stack, you should think of it as a set of algorithms that use the sensors of the robot and the odometry so that you can control the robot using a standard message. It can move your robot without any problems, such as crashing, getting stuck in a location, or getting lost to another position.
You would assume that this stack can be easily used with any robot. This is almost true, but it is necessary to tune some configuration files and write some nodes to use the stack.
The robot must satisfy some requirements before it uses the navigation stack:
The navigation stack can only handle a differential drive and holonomic-wheeled robots. The shape requisites of the robot must either be a square or a rectangle. However, it can also do certain things with biped robots, such as robot localization, as long as the robot does not move sideways.
It requires that the robot publishes information about the relationships between the positions...