Google Alerts

Do you know what is Google Alerts? Why do we use it? Google Alerts is one of Google's services which automatically notifies users when new content from news, web, blogs, video and/or discussion groups matches a set of search terms selected by the user and stored by the Google Alerts service. Notifications can be sent by email, as a web feed, or displayed on the users’ iGoogle page. The service is available to the general public as an open beta release.
Google Alerts only provides content from Google's own search engine.
Currently there are six types of alerts sent when new content matches the search terms of the alert:

• Everything – (default setting) aggregates News, Web and Blogs
• News – sent when matching content makes it into the top ten results of a Google News search
• Web – sent when new web pages appear in the top twenty results for a Google Web search
• Blogs – sent when matching content appears in the top ten results of a Google Blog Search
• Video – sent when matching content appears in the top ten results of a Google video search
• Groups – sent when matching content appears in the top fifty results of a Google Groups search

Users determine the frequency of checks for new results. Three options are available: "once a day", "once a week", or "as it happens". These options set the maximum frequency of alerts and do not necessarily control how often they will receive alerts. Alerts are sent only if new content matches the user-selected search terms.
The first option, for example, means they will receive at most one alert email per day. The "as it happens" option can result in many alert emails per day, depending on the search.
Google Alerts are available in plain text as well as HTML. In October 2008 Google also made alerts available as RSS feeds.

Via Wikipedia.org