Scrum Poker is a tool that can be used in Refinement and Sprint Planning meetings.
Everyone involved in the development of a product takes part in Scrum Poker. Each team member has access to a set of cards through the app (0-40 and special cards). The first step is to briefly introduce a product development element, and all attendees estimate the size of this element by choosing a card from the set. Once everyone has chosen a card, all cards are shown simultaneously and compared with one another. If there are differences, then the team members with the largest differences are requested to share why they chose their own card value. Following this round the process repeats and differences are discussed until a consensus is met. A maximum of three rounds are played, and if a complete consensus is not met in the third round the largest value is taken as the estimate.