@LILY61 I was a professional contractor for 40 years. Cut in is where you take a brush and do your corners first. When rolling you don't want to hit the ceiling with your roller. Also sometimes people do an accent wall. You will definitely need to cut in your edges and corners there too. If you have never done cut in with a brush before I recommend practicing on your wall corners where it is all one color. Try cutting in one side of the corner without getting any paint on the other side of the corner. If you can't do it then get some of the good blue painters tape and tape your corners first. Unscrew all of your outlet cover plates and switch cover plates. Put the screws back in where they came out from. Those small screws are very easy to lose. This way you won't paint any of your cover plates. Remember, two coats is always better.