The dumbbell bench press is a compound exercise that works on your entire upper body, especially the chest, shoulders and triceps.
The movement is similar to the classic Barbell bench press, But using dumbbells has few important differences.
First, the dumbbell bench press requires more stability at the shoulder and shoulder girdle, which helps to strengthen the stabilizer muscles that aren't used with a barbell. Because of the extra stability required, and because your arms can't compromise for each other, you will probably be able to lift less weight than when using a Barbell.
Using dumbbells will allow a deeper stretch at the bottom, allowing you a better range of motion than the Bar. And it will also develop your inner pecs more than the bar that mostly focuses on the outer pecs, giving your chest a more define look in the middle.
Another benefit, is that the dumbbell bench press does not require a spotter. You can simply drop the weights down to your sides, and not risk getting caught under the bar if you reach the point of muscle failure.
Using a dumbbell will allow you to change your grip position (like palms facing each other, a 45 degree angle, etc), This will allow you to target the muscles a bit differently, according to your goal. Also, a different grip angle might help you to put your shoulders and elbows in a more natural position for you, preventing shoulder and joints pain.
Do not clang the dumbbells together at the top. It might feel nice, but the striking of the weights together momentarily releases tension from the working muscles, which you don’t want.
Make sure that you are not holding your shoulders in an awkward position. Be sure to have a natural spinal curve. You do not want to have your lower back flat on the bench, but you do not want to force it to curve too much either.
The dumbbells should be pressing from a far out wide position. Taking them inwards and creating a close grip dumbbell press will only result in excess tricep tension and the chest will become somewhat neglected. Do not flare your elbows completely to the sides though, and keep them in a slight angle (about a 75 degree angle to your torso is a good choice).
Keep a good form and lower the weights all the way down. Remember that a good form is more important than lifting more weight. If your form begins to suffer, or you have a limited range of motion, the exercise is not as effective. Use a lighter weight in that case.