Militia is the armed force of a state. State legislatures usually allowed for different types of militia service, and during the antebellum years most states had a military code which encapsulated current state laws regarding the militia. Companies called into service for terms from ninety days or more were often called State Guards, as they were in Georgia. The law usually limited militia to service within state boundaries and often certain districts within the state.
"Home Guard" is a term applied to ordinary militia. A man didn't enroll in a local militia company; he belonged by virtue of his residence. That's why militia districts are identified. These men remained at home until a call by the governor. Service was more or less like jury duty with one exception -- a call was issued to all men living within certain districts. These calls would be for service within a county or congressional district as described by law.
During the Civil War Southern governors used local militia for law enforcement purposes. This was a great need in most districts. Sometimes home guards applied summary punishment and not just apprehension and arrest, as their duties specified. State Guards were posted at bridges, depots and other important points for communication and transportation.
Finally, a militiaman was not a Confederate soldier. In most states militia service alone did not qualify a man for a pension. A letter written by a Confederate veteran to the Alabama pension board made a strong case as to why a soldier's service in the field should not be made equivalent to that of a home guard.