Grouping is when you have to terms that are the same inside the parenthesis and a different or same number outside the parenthesis and then the one inside the parenthesis u are going to group them not combined them and write them once and the numbers inside the parenthesis group them together by adding them and put parenthesis between them
Grouping can mean different things in different contexts. In simple cases, polynomials are written in such a way that all you need to do is add parentheses to make groups. Usually we are interested in doing this so we can factor or simlify the result.
Example x^2 +2x +3x +6 (x^2 +2x) +(3x +6) . . . . parentheses added to group pairs of terms x(x +2) +3(x +2) . . . . . . common factor pulled from the terms of each group (x +3)(x +2) . . . . . . . . . common factor removed to give factored result