Creating a channel trailer is rather important as it'll be the first video people who are new to your channel see when they go to it. A short and sweet video always does the trick. If you want, you can simply just explain to them what it is you are about, and what they can expect to find on your channel. However, an even better way to tell them, is to show them! Make a short montage, or utilize your skills in a way that show them what it is you do!
I've had a few channel trailers now, since I had to go back and fix things. So far, no complaints, haha.