For every major itteration of the Android operating system, google chooses a dessert/sweet food name that starts with the next letter in the alphabet.  The first two (unreleased) versions were alpha and beta (typical in the tech world), then, 1.5 Cupcake, 1.6 Donut, 2.0/2.1 Eclair, 2.2 Frozen Yogurt (often referred to as Froyo), 2.3 Gingerbread, 3.0 Honeycomb (Tablets only), and the latest (not officially on any released phone yet) 4.0 Ice Cream Sandwich.