Licensing is selling reproduction rights for a specific image, on set product/s, for a set period & territory e.g. for cards, on a 3 year license selling in UK & USA. Payment is often an advance on royalties based on sales. Licensing as opposed to selling an image outright enables artists to retain copyright & benefit from selling the same image more than once e.g an image sold with first rights for editorial can be licensed again for pop-up books etc. Here are a few examples...