Describes the way Houdini is built.
Maya and 3ds Max are both flat; Houdini is not. Houdini’s internal architecture is an actual file system. There are folders, and in those folders there are files (nodes, scripts for each node to record the node’s state, the network state and more). You can also have folders in folders thousands of layers deep. For example, when building characters, you can put everything into an Subnet node and turn it into a digital asset representing your character. Then you can copy and paste the character as many times as you like with no name clashes.
Expressions that reference other nodes and their parameters take on the familiar unix like path structure. For example, /obj/my_object/tx would be an absolute path and ../COG_root/tx to reference the tx position parameter of another object sitting in the same network called COG_root would be a relative path.