The backlog grooming is intended for making sure that the team has the backlog which is relevant, detailed and estimated to a degree appropriate with their priority. In the backlog grooming meeting, the scrum team sits TOGETHER to discuss the items from the product backlog and this meeting is done on a REGULAR basis to keep the backlog healthy and up-to-date. 

They pull the items as per the priority order and refine them with rigorous discussion and brainstorming. They even TALK about the blockers that might come up in their way and also the dependencies, whether it is upstream or downstream. In the backlog grooming the team takes up an item from the backlog and discuss how they can work upon it, they even talk about the ways of IMPLEMENTATION. This meeting gives the team the TIME they need to understand new stories before estimating and working additionally providing time to optimize the design. It also helps in streamlining the planning meeting by saving the hours the team would have spent. By devoting time to backlog upkeep, the team safeguards that this preliminary planning occurs prior to the sprint planning meeting.