There are as many types of monitor arms as there are monitors, but, as a general ergonomic principle, you need to be able to raise and lower your monitor, to keep it at a comfortable eye level to prevent neck strain, and to move it throughout the day to prevent yourself from staying in the same position for too long.
Aside from height, depth and angle adjustability, an articulating arm eliminates clutter by affording you more desk space, and they help to manage unsightly cables. For users of our adjustable height desks, we highly recommend adding a this accessory.
Use of a monitor arm can offer a more comfortable working position as well as free up valuable desk space. For factors you should consider read this Article on correct monitor positioning.