I have never heard of tagging. But I learned now tagging is assigning your own keywords to things online like photos or blog entries so you can categorize them and locate them easily in the future.
For example, del.icio.us –
"…is a social bookmarks manager. It allows you to easily add web pages you like to your personal collection of links, to categorize those sites with keywords, and to share your collection not only among your own browsers and machines, but also with others."
I haven’t tried it yet but seems really useful!
