What are smart tags? From the Microsoft Excel Help file:
"You can save time by using smart tags to perform actions in Microsoft Excel that you'd usually open other programs to perform"
For instance, if you have a spreadsheet that computes market capitalization of a group of firms, this can be automatically updated with current share prices and current shares outstanding.
How do you do this? From the pull down menus, go to Tools, autocorrect options, smart tags.
A quick internet search shows that these smart tags have created some enemies since Micorosoft chooses the web site (MSN in this case) they send you to for the data and may even be able to track your usage, but that said, the tags sure are useful! and you can turn them off easily enough.