Describing users tasks has been the focus of research for many years starting with the seminal work from Annett and Duncan in 1967 [2]. Since then, the Human Factors and Human Computer Interaction domains have proposed multiple contributions identifying the elements that have to be gathered and represented in order to describe precisely the relevant aspects of users tasks. This keynote will highlight these fundamental elements of tasks descriptions and will state the current state of the art. A specific view on how to use such descriptions to design and assess automation will be given. Some publicly available tools will also be presented together with their use in various industrial application domains. These applications will be the opportunity to identify remaining research challenges for tasks description and modeling.