on Jane Friedman site:
Receiving a R&R from an agent or editor can be both confusing and exciting at the same time. It might feel a bit disappointing because you were hoping for an offer, but let there be no mistake, an R&R is good news. The agent sees something in your work, and they are inviting you to submit again. They have taken time out to read your pages and provide notes to help you improve your manuscript. R&Rs don’t happen to everyone, and an agent doesn’t send them unless they’re genuinely interested.
An R&R is a fabulous opportunity to show agents or editors your revising skills and how you interpret their feedback. First and foremost, it provides agents and editors with insight as to how you handle revisions.