In the Volume Medium Tab you can make many adjustments to the absorption, scattering and emission options as well as the Material Volume options. Whether you use a generator or a VDB, you have to make the final look settings for the volume. And since these settings are related to each other, it is not possible for us to give you a full description. Unlike the material volume, all of these options work based on the Voxel Grid this time. The Ray Casting method interacts with these Voxels and voxel grids and collect necessary data for final render. We can say that the most important parameters here are the "Step Lenght" and "Density". Especially the step length can change the appearance of the volume dramatically. For example, when you use smoke VDB, you can play with the step length setting to show this smoke as dense or misty depending on the channel parameters. Do not increase it too much because after a while it will be calculation to nothing and you'll waste your time. Generally keeping this value low will produce quality results.  

Our recommendation for this section is that you will be practicing constantly because the variables according to the simulation are infinite. In Volume Effects section you will see the practical use of all the options.