A cavalry mount is the most straightforward thing a character can ride – this category includes things like horses (and their mechanical or undead equivalents), giant wolves, boars and other horse-sized or shaped steeds. As with the definition for the cavalry troop type, a cavalry mount's key definition lies in the fact that it has only a single Wound. Therefore, if a character is riding a mount with a single Wound, he is riding a cavalry mount.
If a character has a cavalry mount, the whole model is treated as having the troop type 'cavalry' and follows all the rules for both characters and cavalry models.