In my opinion, the volley is the easiest tennis stroke to learn and teach.
This is because of its simplicity and the fact that it has the fewest technical elements to consider.
However, aside from the technical aspects, there are also tactical considerations. In this regard, we can identify two main types of volleys:

• The Low Volley: This volley involves making contact with the ball below the net level.
• The High Volley: This volley involves making contact with the ball above the net level.

The Low Volley:
Technically, you want to keep your racquet head and your… head/eyes together. When the racquet head lowers for the below-the-net ball, you must also lower your head. Imagine the two “heads” being connected by a string: when one lowers, it pulls the other down. This head lowering should be achieved by bending your knees, not your back, as demonstrated in the video below.
Tactically, the low volley is a setup or placement shot. You want to get it over the net and place it strategically, ideally deep. However, you can also attempt a short angled shot only if you believe your opponent will have difficulty reaching it.

The High Volley:
This volley is, or should be, an aggressive shot because you catch the ball above the net level and can hit it with more power.
Technically, swing the racquet from high to low with a shortened swing (for more control) and transfer your body weight into the shot to generate the necessary power.
Tactically, go for angled winners. If you cannot finish the point with the first shot, you should be in a position to do so with the follow-up.

A third volley shot could be identified if you consider the one you contact at the waist or net strap level, which can be hit deep and aggressively. From a technical and tactical standpoint, I would categorize this with the high volley.

I have recorded a video for you to see and compare the two main types of volleys: low and high. Check out the video and let me know in the comments section below if you have any problems with this shot. I would be happy to provide tips and help you improve it.