A feed is an easy to use way of keeping up to date with lists of information on the web.

You normally subscribe to a feed using a feed reader which collects together all the feeds you subscribe to and also provides a way of unsubscribing should you get tired of a feed. Many browsers have feed readers built in, as do most email clients. In fact, a good way of thinking about feeds, is as a cross between subscribing to an email newsletter and regularly visiting website's news section.