A lid is basically a non-beveled-edged disc. The name implies that it looks like the lid of a container, like a tub of margarine, a jar of pickles, or a can of Pringles. They're usually large diameter (many believe it's a requirement), but there are some modern golf-disc sized molds like the Polecat or Rattler. The Zephyr, Ultrastar, Gopher, and Whittl'r (or however it's spelled) are all great examples of lids.
Similar to lids, you have fastbacks. They typically aren't beveled-edged either, but they have a raise in their flightplate. The Sonic and Bite are great examples.