What can you do with Ajax?

• Partial update of page
• Periodic polling for new/changed data
• "Event"-driven interaction (instead of 'form submit'-driven)
  • click, mouseover, submit, etc.
• Incorporate data and functionality from other sites into your web site
  • Your data + functionality from elsewhere
  • Your functionality + data from elsewhere

Ajax is a term coined around 2005 - see Ajax:  A New Approach to Web Applications by Jesse James Garrett