Aggregators reduce the time and effort needed to regularly check websites for updates, creating a unique information space or 'personal newspaper'. Once subscribed to a feed, an aggregator is able to check for new content at user-determined intervals and retrieve the update. The content is sometimes described as being 'pulled' to the subscriber, as opposed to 'pushed' with email or IM. Unlike recipients of some 'pushed' information, the aggregator user can easily unsubscribe from a feed.
Aggregator features are frequently built into portal sites, Web browsers, and email programs."
