A story or task aimed at answering a question or gathering information, rather than implementing product features, user stories, or requirements. Sometimes a user story is generated that cannot be estimated until the development team does some actual work to resolve a technical question or a design problem. The solution is to create a “spike,” which is a story whose purpose is to provide the answer or solution. Like any other story or task, the spike is then given an estimate and included in the sprint backlog.