Table of Contents Alerts (TOC)
A table of contents alert emails you the table of contents when a new issue of a specified journal is published.
Database Search Alert
A search alert notifies you (either through email or a RSS feed) when new articles matching a customized search are found. You can specify how frequently you'd like to receive search alert notifications.
Citation alerts are less common. A citation alert emails you each time an article you selected is cited in a new publication.
Web Page Alerts
A web page alert notifies you when a web page has been updated.
Twitter and Facebook
You can follow journals and bloggers on Twitter and Facebook for alerts when they update their websites.
RSS Feeds are subscriptions to websites or journals than you can read in a news reader.