Instead, we will talk about the small set of USB classes that are most used by USB device developers:

• Communication Device Class (CDC): e.g. those "Fake Serial Port" chips
• Mass Storage Device (MSD) class: e.g. thumb drives
• Human Interface Device (HID) class: commonly associated with mice and keyboards, but really the most highly developed USB class there is

We'll also talk about one other option that microcontroller folks often use:

• Classless Bulk devices: sometimes called "generic" devices.  (No class at all!)