You hook it up to the network to use monitoring features like a remote camera view to make sure your print is going smoothly.

SD cards work but it's extremely less convenient than just printing straight from the slicer.

You can use any slicer you want but Bambu wants only their slicer to directly connect.

CLI slicing is not something you want in general. Visual confirmation of the toolpaths is very important to making prints as successful as possible.