RSS stands for 'Really Simple Syndication' and basically it is a file created by a website (like the one created by HubPages) that contains all your latest content in heirarchical fashion.
RSS is used as the primary method of collection and accumulating content, aggregating. So, someone can subscribe to a RSS feed using a Feed program, Google Reader or sometimes their web browser and then go to that program to read all your latest content.
In terms of bringing traffic, RSS feeds can't bring new traffic, but can bring traffic back. So, if someone likes your stuff then they can subscribe to your feed, they then see all your latest content and keep coming back to your new hubs!