To explain it quickly, the service takes your RSS feed of news or blog posts, syndicates it within the GetResponse system, makes an email newsletter out of the posts (as chosen by parameters set by you), and sends it out to all your subscribers on a set time schedule. Here is their own announcement blurb:
With the new RSS-To-Email, you are in total control. You have free reign over how frequent the mailings should be. Email your subscribers every time you post a new blog article? Easy! Prefer to send a nice daily digest with most commented articles? Boom, it’s done. Fancy a weekly or monthly digest instead? Be our guest.
The service is currently being labeled as beta, which generally means it could have a few unresolved kinks that are common to any new product launch but should work without a hitch for most users. There is currently no additional charge to use the service, and it's available to all current subscribers.
If you don't have an account with GetResponse and you are interested in seeing what it's all about (check how quick it is to send out a newsletter!), be sure to click the link and take their free 30-day trial (no credit card needed!)!