From Google's website:
Google Alerts are email updates of the latest relevant Google results (web, news, etc.) based on your choice of query or topic.
Some handy uses of Google Alerts include:
* monitoring a developing news story
* keeping current on a competitor or industry
* getting the latest on a celebrity or event
* keeping tabs on your favorite sports teams
Depending on your niche and your online business, you may want to set up Alerts on each of your major keyphrases, your own name, your website's name, your competitors' names and sites, etc.
Google Alerts are handy for coming up with content ideas, product ideas, possible joint venture partners, and much more.
You can always manage your Alerts to add and delete items.
Go to http://www.google.com/alerts to sign up for Google Alerts.