Mise en place (pronounced meez ahn plahs) is French for “everything in its place.” It refers to the art of gathering all the ingredients needed for a recipe and prepping them (veggies chopped, spices measured, etc.) before you start to cook. (Think TV chefs who often have everything they need in ramekins or small bowls.) Aside from just sounding fancy, getting your mise en place together will make you a better cook. Prepping all your ingredients will require you to read through at least the first half of your recipe — the part that lists the ingredients and how they should be prepared. You’ll know before you start whether you have all the ingredients you need.
It may be tempting to chop the carrots while the onions are sauteing, but you’ll save time by prepping everything first and once you actually start cooking, you can focus completely on the task at hand.