This post is from allaboutagile.com by Kelly Waters.
A software release may result from multiple iterations (or ‘Sprints’ in Scrum).
Sprint Planning is about planning what’s included in the next iteration.
Whereas Release Planning is about planning multiple Sprints, in order to predict when a release (or releases) might be delivered.
Release Planning is a very simple way of doing some top-down planning. Much less complex than a more traditional project plan on a Gantt-chart. Therefore much quicker to do. And, I would say, no more or less accurate.
Click here to see the full post.