Dear Mr. Horton,
The difference between a Cavalry and a Mounted Infantry Regiment is predominantly in mission. Their Table of Organization was largely the same but often the were armed with heavier weapons (i.e. rifled muskets versus carbines and pistols). The role of the Cavalry is to conduct reconnaisance, security, and economy of force missions for the commander of the unit it supports. The mounted infantry primarily focuses on mobility, shock, and firepower. A good example of this type of force is Colonel John T. Wilder's Lightning brigade. General Nathan B. Forrest is an example of a force transitioning from a traditional cavalry role to one of mounted infantry. Look at him during the Chickamauga Campaign. The mounted infantry had the mobility with their horses but once they arrived at the point of contact they dismounted and fought like typical infantry. I hope this helps. Please let me know if you have any questions.
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment