In a nutshell, Lightroom is a program that can manage and edit your images. The catch, though, is that it doesn’t really edit your images, or actually manage anything either. Instead, the program works by looking at pictures you have stored on your computer, and allows you to create instructions for how you want to change them.
Lightroom can be your best friend, so long as your career isn't in photojournalism. Then you might tread lightly on using this.