You can search "Colonial Train Band' in any search bar, suc as google to get definitions/descriptions.Here are 2 examples below.
'The earliest and most important branch of the Colonial militia was an infantry company known as the train or training band. At first, all men liable for military service were formed into the town train band. They were required to have a musket, bandoleers, two pounds of powder and 120 bullets. Bands usually consisted of 64 men. Large towns had several bands. Members were fined for unexcused absences.'
'Train Bands From the first, the Puritan settlers of New England had to organize their defense, particularly against the Indians. They did so in the English way, not by standing armies but through the train band militias, at times organized and trained by a handful of veteran soldiers who were paid for the task.
The New England militia train bands democratically accepted just about everybody from the first. Moreover, in the spirit of Puritan covenantalism, the train band was based on voluntary consent. The train bands were covenanted organizations by design, one aspect of which was the selection of their own officers. This power evolved over a period of years but it came to be because it fit into the general pattern of civil and ecclesiastical elections in the colony. One qualified as a militia participant by taking the oath of fidelity which was viewed as the basic act of consenting.
A different type of force emerged in the 1670's. Hired volunteers ranged the frontiers, patrolling between outposts and giving early warning of any Indian attack. Other volunteers combined with friendly Indians for offensive operations deep in the wilderness where European tactics were ineffective. The memoirs of the most successful leader of these mixed forces, Benjamin Church, were published by his son Thomas in 1716 and represent the first American military manual.'