A 'motion' is a formal request to the court to take some action.
A 'motion to consolidate' is a request to join two lawsuits together.
This can happen when you have started a lawsuit and soon realize that there were more people involved in your accident or medical negligence or wrongful death matter than you originally thought. In that case, you may have to begin a separate lawsuit against those other individuals or companies and then at a later time ask the judge to join these two cases together.
This will only work where both cases arise out of the same set of facts and the issues are all related.
When the court approves putting the two cases together, the name of the lawsuit gets combined and is assigned one identifying number, known as an 'index number' instead of two separate numbers.