Houdini no longer has SHOP networks. Materials are now built from pure VOPs.
Channel nodes create, filter, and manipulate channel data.
Composite nodes create, filter, and manipulate image data.
Dynamics nodes set up the conditions and rules for dynamics simulations.
Object nodes represent objects in the scene, such as character parts, geometry objects, lights, cameras, and so on.
Render nodes either render the scene or set up render dependency networks.
Geometry nodes live inside Geo objects and generate geometry.
Containers for VOP networks.
VOP nodes let you define a program (such as a shader) by connecting nodes together. Houdini then compiles the node network into executable VEX code.
TOP nodes live inside TOP objects and do work.