The term 'USER-friendly' (easy to operate) can be described as a product or service that is easy to use and understand. It is designed to be intuitive and require minimal effort from the USER. USER-friendly products are often designed with the USER in mind, taking into account their needs and preferences. This term is often used to describe technology, such as computer software, but can also be applied to other products and services. The four letter solution for this crossword is USER.