A widget is a little thing that you can stick in a blog or something that will direct people to your site. I could take my widget for my hubpages and put it on my blog, then everyone who reads my blog will also see the widget and it's like advertising for myself. It's basically a way to advertise yourself on other sites you own, or if say you were good friends with someone from hubpages you could put a widget of theirs on your side if you wanted to promote them... I think.
Sorry it took so long to get back to you on this but I didn't really know either so I had to go look it up. I hope this helped.