In the video, the process of factoring trinomials is described. A trinomial that cannot be easily factored in its original form is shown. It is simplified by pulling out the greatest common factor. After that, a trinomial that is easier to factor is shown. Next, the simplified trinomial is broken up into four terms so that factoring by grouping can be done. Once again, a common factor from each pair is taken so that two binomials are created. Once the greatest common factor is added back with the binomials, factoring the trinomial has been achieved through the greatest common factor and grouping.