True Saddle Discomfort is when the symptoms you are experiencing are directly related to the type of saddle you are sitting on. A good place to start when deciding which saddle you need is by measuring the width of your ischial tuberosities (sit bones). Getting the right width saddle will ensure your sit bones will contact the saddle in the correct area.
You should also consider the profile of the saddle. This is the shape you see when looking at the saddle side-on. As a rule of thumb, flat saddles are more suited to aggressive positions, whereas rounded saddles are more comfortable for riders with a more relaxed riding style. Although this is a general rule, it is not always the case and trialling a saddle before you purchase is a good idea.
Saddles with cutaways in the centre can be useful if you suffer from numbness in your nether regions by releasing pressure from the nerves in that area. Split-nose saddles are helpful for people with a leg-length discrepancy or an asymmetrical pedalling action.