Like any hyped technology, Web 2.0 has a lot of buzzwords. They include the tag (as in tag cloud), the folksonomy, the long tail (more about that in a later post), and social software.
Social software is there to support networking and social activities via the internet. Lots of people spend lots of time interacting with friends online, whether they’ve ever met them in person or not. For people who are embedded in that world, it’s a natural way to interact. For everyone else, it can be slightly creepy to think that complete strangers read everything you write and know a lot about you. Lots of real-life friendships have blossomed from online activities, and more than a few problems have occurred as well. The social aspect, that is people interacting with other people, is probably the most important aspect of Web 2.0 sites.
The idea behind tags is to label things, so they’re loosely related to categories or (even more loosely) ontologies. Tags typically aren’t applied by specialists; in keeping with the Web 2.0 philosophy they are applied by the person writing the blog post, or uploading the photo, or storing the bookmark. So you get near-duplications, misspellings, incorrect usages, double meanings etc., but at least you do have some sort of categorisation applied to these bits of content. And many people go to quite a lot of effort to see what sorts of tags other people use, and then pick the same ones where possible. This then ends up being a folksonomy.
This image shows a tag cloud, which is a collection of tags where the tags in big fonts are the more important ones (usually means they show up more often). Unlike say topic maps or RDF, the spatial distribution of the tags doesn’t usually mean anything, although in theory you could use it to show relationships between the tags. Since generally there is no formal relationship between them (other than that from natural language) this would be tricky to automate and most people just fiddle with the cloud to make it look nice.
The other buzzwords on the slide are the important ones from a couple of years ago, these days there would be a few more. There’s also a version of the slide with the words linked to the relevant Wikipedia articles.