Volley
The volley can be one of the trickiest strokes in tennis. This is because a volley is typically hit close to the net, causing players to have to react quickly to shots. The volley should just a simple "punch" of the racket straight forward. It doesn't require you to swing all the way through, if you do this, most likely the ball will always go out of bounds or into the net. In volleys, if you are going to hit it on your dominate hand side, use one hand, punch the ball forward, and step forward with your left foot. If it is on your non dominate side, you are going to put two hands on the racket your non dominate hand on top, while your dominate hand is below it. As you punch, step forward with your right foot this time. The volley is used more in doubles, because one player is closer to the net during a point. However, once a player gets the volley down, it can be an awesome stroke, and fun to use.
Forehand
The forehand stroke is the most basic stroke seen in tennis, it is also referred to as a ground stroke. This stroke is a one handed stroke that is hit with a player's dominant hand. Many players prefer to hit with their forehand, because it is their strongest hit. Unlike a volley, a ground stroke is one where the ball bounces before the player hits it.
Backhand
The backhand is just the opposite of the forehand. The back hand requires two hands to hit the ball on the player's non dominant side. The back hand can usually be a difficult shot for many to become consistent at simply because one has to be sure to get the proper technique.
Overhead/Serve
The overhead shot is exactly as it sounds, an overhead hit. Although this shot seems like it should be pretty simple, it can be tricky. An overhead is usually hit somewhere close to the net, when the opponent has either purposely or accidentally lobbed the ball. An overhead is just like a serve except a serve obviously is further back and you get to throw the ball up. The key to an overhead hit is to tuck the racket back behind your back before making contact and then swinging through the ball while keeping your eyes one it. The serve can be a little more tricky, but is the same concept.
This instructional video is awesome at explaining these many strokes thoroughly while also giving you visuals to proper positioning.
Here is also a great website for further explanations about the strokes of tennis:
