To learn about coffee, you can take one or both of my classes, come to one of my public lectures, explore my coffee web site, browse the coffee holdings in the Maxwell library, or sign up for classes through the Barista Guild of a America. Or you can just study the infographic below, lifted shamelessly from Daily Shot of Coffee. Which raises one more possibility: subscribe to Daily Shot for ongoing coffee education.
I would quibble with only two items in this graphic. One is the suggestion that arabica and robusta are the only species of coffee (genus Cofea). In reality, robusta is the most common varietal of canephora. Two other species are grown commercially, though the amounts are tiny and some experts consider liberica and conillon further varietals of robusta. Most agree that these are terrible coffees! My friend Freddy in Nicaragua informs us that there are about two dozen species, most of which are not commercial, some of which are found wild in the Americas, indicating that the genus was present prior to the emergence of the Atlantic Ocean.
The other is the rather confused terminology used for civet or Kopi Luwak coffee. These are not varietals, but rather a very rare method of harvesting and processing coffee -- using the palm civet digestive tract. Almost all of the 500-600 pounds of coffee collected in this manner each year comes from Indonesia.