Mise en Place is a French culinary phrase which means "put into place" or "everything in its place". It's the smart way to begin your cooking and to make every step as efficient as possible.
It will prevent you from getting halfway through a recipe only to find you're missing one key ingredient. With the help of some handy preparations, when the time comes to combine the ingredients on the stove or assemble the final dish, you aren't scrambling to dice your onions or chop your parsley while something is cooking and maybe burning because of your lack of attention.
While mise en place won't prevent you from drying out a roast or burning a batch of cookies, it will make you a better cook by changing the way you think about and work through preparing a meal from start to finish. By practicing the organizational skills of mise en place it will greatly improve your home cooking experience.