Peds are socks that come up to the ankle. They are typically worn by women who want to look like they're barefoot in their shoes, but they're not. I'm not sure what the real goal is -- maybe to show as much leg as possible or to minimize tan lines or something. When I was younger, girls would wear Peds with little cotton balls or pom-poms at the heel. I used to be able to annoy my little sister by sniping them off or drawing smiley faces on them. I don't see those types of Peds around anymore.
Even though "Peds" is used generically, I think it really is a brand name.