During Sprint Grooming groups of features or Epics are broken down to user stories by the Product-Owner,,,, ; then Spring Planning is used to estimate the amount of efforts on completing a user story through tasking with the Scrum Team;)
During Sprint Grooming, groups of features / requirements, or Epics, are broken down into user stories by the Product Owner. Then Sprint Planning is used to estimate the level of effort to complete a user story through tasking by the Scrum Team.