How does a sculpted model relate to topology?

I’m a beginner and I want to model a human head, and the tutorials I’ve seen show you how to do this by starting with a cube then subdividing & sculpting, so I did it like that. But then I saw the word “topology” somewhere, so I watched a bunch of topology tutorials…and now I’m confused about the correct way to start an organic model, because after the subdividing and sculpting, you have a gazillion little surfaces which have no topological flow. Are you supposed to take all those lines and clean them up until there’s good topology? Or is that subdividing & sculpting method useless for topology, and you’re supposed to construct the topology with just lines in space or something?

All the topology tutorials I’ve seen talk about what “good” topology is and how to tweak it, but they never say how they made it.

It depends what you want to do with the sculpted model. If you want to animate it you should really retopologise the mesh after sculpting. If you just want to render it then who cares what the topology looks like as long as the render looks ok.

There are a number or retopology tutorials on blendercookie

Retopology–so that is, you do go through that sculpting process, and then you use what you’ve sculpted as a base for creating the topology?

yes. the shulpted model acts as a base you then remake the topology on top with clean lines and good edge flow ( which you’ll find out about on blender cookie) the clean mesh is then mapped to a 2d surface in a process called UV unwrapping. once that is done you then tranfer the fine details of the sculpted model onto the 2d map with a process called baking you then use the baked map as a texture to give your clean topology the detail of the sculpted model.
you can then delete the sculpt as its no longer useful.

okay, thanks so much

There are two kinds of sculpting systems in Blender you can use: dynamic topology and multiresolution.
Dynamic topology triangulates the mesh and subdivides areas dynamically. You could use that to get most flexible way of sculpting a shape (and shape only).
Multiresolution sculpting subdivides faces on the whole model, which means that you need a good base mesh to control the polygon density if you start your modeling process with that. You could also use multiresolution sculpting for detailing after doing a retopology pass because it preserves UVs and the topology you’ve created.

Topology is too wide subject to explain thoroughly in a thread but I’ll try to explain what it means, briefly.
Polygon model is a basis for everything that comes after modeling in a 3D pipeline (texturing, rigging, animation, lighting, rendering, post-processing). Topology is the built-in aspect in a polygon model that enables functionality for those steps, depending on the end goal (game model, high detail rendering, high-res animation, etc). The universal function for topology is to describe shapes the model has, whether or not those shapes stay still or are created by moving the vertices. You would also use topology to build better topology until it’s in a state it fulfils the set requirements, which is what modeling essentially is.