Quite confused. Read the documentation

http://www.sidefx.com/docs/houdini/dyno/cache [www.sidefx.com]

but still don't understand the difference between ‘baking’ a simulation and caching a simulation to disk in the cache tab of your DOP.

Aren't they the same thing?

Can anyone clarify? When you cache to disk, isn't the cached sim data saved between sessions?

Baking is the actual process of calculating a simulation, caching is storing the result of the baking process. Either on disk or in memory.

So yes if you cache to disk and set the “load from disk” option to on the next time you open the scene it will use the disk cache. If a sim is only cached in memory and not on disk, it is lost on the next start.

There's also “cooking” and that is Houdini calculating the result of a single node. Cooking and baking or somewhat interchangeable if I'm not wrong. But the latter is mostly used to calculate a timerange.