They pretty much say it all here on their blog.

Netvibes is an AJAX dashboard and homepage, similar to Google, Yahoo and Microsoft's offerings, with a rich set of powerful modules. I like the organization of widgets into separate tabs (for the most part). It lets me keep all of my important feeds, email and a calendar on a frontmost widget, and lesser feeds and views elsewhere. I even have a whole tab of Liberatr.net feeds so I can make sure they are all running smoothly.

Adding Meebo to your Netvibes is accomplished by adding an entire tab that the AJAX-based mult-platform IM client lives inside. There is support for AIM, YIM!, MSN Messenger (even though Y! and MSN work together now) and Jabber/GTalk out of the box. Since meebo lives inside a browser anyway, this is a great match.

Alexa is a well-known publicly available web ranking and traffic site with an API which allows for widgets like the one being supported by Netvibes. Alexa's data is not widely regarded as the most accurate, but the fact that it is free and public makes it some of the most referred to information on the web. The Netvibes tab allows you to track the traffic of up to 5 sites on a graph. This wil be great if I ever get a site listed there. Right now, I have my Feedburner stats in a widget to let me get a quick glance at how my feeds are doing today. I wonder if anyone makes a Mint widget...?