robertharding offers images & video in two distinct flavours 'Rights Managed' and 'Royalty Free', the two licences have differences explained below.
Rights Managed (RM)
A Rights Managed license is widely used for commercial transactions. An RM license includes a fee structure for use of the image, as well as possible restrictions on how long the image can be used, where it can be published, the type of media in which it can appear and the size and resolution of the image.
Royalty Free (RF)
A Royalty Free license is much less restrictive than an RM license. A user pays a one-time fee for a royalty free license and can then use the image/video as many times and in as many places as they choose. The "free" in royalty-free does not mean there is no cost for the license, but instead refers to being able to freely use the image without paying additional royalties. A small-business owner, for example, may opt to pay a one-time fee for RF images for his website.