Quick Definition: The speed at which you speak, combined with accompanying tone, volume and inflection.
Cadence has to do more speed, and rather, the pattern of your speech. The volume, tonality, and the overall range you have in your voice that gives you character and personality. Great entertainers, hosts, Regis Philbin have voice cadence.
Speech cadence is related to story telling, vibe projection as well as body language. There are a lot of things you can do with cadence. Mastering this is super important to becoming an awesome guy. A lot of guys have a hard time switching to strong cadence from their normally weaker voices, and this is ok. Try practicing in front of the mirror or when you are alone. Some of the best political orators have practice speaking in front of the mirror, or in private. As with all skill-sets, practice makes perfect.
Try working on your speech by having some cadence to your tonality.