From the introduction:
In Japanese you usually refer to other people with some kind of suffix after their name. Members of certain scholarly professions (most notably teachers, but also writers and doctors) get -sensei, and most people get the basic -san. There’s also a diminutive name suffix, which is -chan; it’s usually used to refer to cute animals or cute girls. Never daunted by the limitations of language or common sense, Japanese otaku have devised a sort of second-stage diminutive suffix; -tan (or たん if you want the Japanese writing) is a baby-talk version of -chan, and the preferred name suffix for mascot girls.
-tan is not pronounced like the color that’s a sort of light brown and rhymes with man. The letter A in romanized Japanese always has an “ah” sound. A like in “father.” Got it? Good.