Most is based on personal experience making meads, wines, and ciders. The intent is to use as little special equipment or ingredients as possible, using whenever possible those things easily obtainable at a grocery store or hardware store. Some recommendations are made for things that may be bought at a beer or wine making supply store, but all of these suggestions are optional. The process of fermenting is basically feeding sugars and nutrients in solution to yeast, which return the favor by producing carbon dioxide gas and alcohol. This process goes on until either all the sugar is gone or the yeast can no longer tolerate the alcoholic percentage of the beverage.
Different yeasts produce different results, and have different tolerance levels.
Yeast can't live on sugar alone. It is happiest when it has a real organic soup of acids and nutrients and minerals, like any other living thing. Bacteria also like oxygen, so while it is good to agitate the solution before yeast gets added so the yeast can be fruitful and multiply, it is best to keep as little oxygen from getting to your beverage after fermentation has started. Honey has a lot of what yeast needs, but is somewhat resistant to being fermented by itself. A pure honey solution will ferment, but it can take three months to a year to ferment.