In my county (Camden County, New Jersey), there are many different kinds of Christian churches: Catholic, Presbyterian, Episcopal, Methodist, Baptist, etc. There are orthodox, conservative, and reform Jewish synagogues, Muslim mosques, and at least one Hindu temple. Why am I talking about churches? Because these different houses of worship reflect the vast variety of types of worship engaged in by my neighbors.
Cantons could be considered the political equivalent of houses of worship. There is no set number of potential cantons, just are there is no set number of types of churches. Each canton has members who ascribe to a particular set of principles and values regarding public life.
A canton (as it is used here) is a voluntary association of persons, similar to a political party in that the members share similar values and principles, but different in that, rather than working to have someone elected to a representative body, the chief member of a canton, called a Champion, becomes the representative for the members of the canton in a representative body. Thus, instead of the people of a Congressional District (for example) with many different political philosophies electing one person to represent them all, people of the same political philosophy join a canton that represents their values, and the Champion of that canton becomes their chosen representative. The collection of Champions constitutes the representative body.
Here’s what is meant by a “representative body”. Wherever you have taxes in a territory with a representative form of government, you have a representative body. In the US government, that body is called the House of Representatives, each member of which represents (in theory) the people of a congressional district within one of the 50 states. But almost every level of government has a representative body. In a city, they are often called City Council. In a county they go by many different names: “Counties are usually governed by an elected body, variously called the county commission, board of supervisors, commissioners’ court, county council, board of chosen freeholders, county court, or county Legislature.” 
Canton forums, the collective name for a group of Canton Champions within a territory, would replace any of these forms of representative body, and in doing so would provide “True Representation”.