If you tow a trailer regularly, you should consider using sway controls. The video gives insight into how to best use these controls. The narrator focuses on ready-made sway controls that have ball mounts with the sway control jacket already on, which makes for easy installation and use.
Even if the trailer is light and easy to tow without difficulty, things can get difficult on the open road. There is always the chance of strong cross-winds and other events that can disturb the stability of the tow.
Putting a trailer hitch sway control on and applying moderate tension will remove a lot of the sway and make your trip safer and more comfortable. If, at some point, you enter a more congested urban environment that requires you to back up or maneuver around tight corners or through parking lots, you can release some of the tension on the control, which will allow the towing connection to move a little more. When you are ready to hit the open road again, you only need to restore the previous tension.
You should be as safe as you can when towing your trailer. Sway controls give you the means to do so. Now you know how they work.