When an image is available in public domain, it implies that it can be used free of cost. The user does not need a license for using them. These images can be used for commercial and personal purposes.
A rights managed image is one in which the way to use it is specified by the stock agency. For instance, the image size and resolution, geographical area of usage, the length of time of usage, may be specified. It can be used by a single user or multiple users.
There is a greater flexibility offered when Royalty Free images are used. Royalty-free implies paying a one-time fee for non-exclusive lifelong use of the image. You can decide how to use the image, how many times to use it, how long to use it, the number of projects you can use it for, etc. You only need to conform to the license agreement.