This is a great exercise for the lower chest area. It's not for beginners because it does require some pre-conditioning and experience with using the dumbbells. Thus, if you're a beginner you should do this same movement but with a barbell.
This exercise is what will give you that much-coveted bottom chest line that sort of "frames" and outlines your chest on the bottom.
Keep in mind that this exercise is really not about going extra heavy with the weight, it's more about the movement and executing it right so that it has maximum impact on your lower chest. Furthermore, you need to make sure that this exercise is done in conjunction with chest exercises that work your upper chest. You don't want to be only building your lower chest muscles because then you will have a weird-looking chest slope.