Nutrient timing is about When you are eating (during your workout, post workout etc..) For regular gym goers and people who are looking for general health and weight loss/ fat loss nutrient timing is a matter of preference and can help, but only if you have the other important aspect’s of your eating down first. Eating real food, portions etc..
For the endurance athlete though it is very important. Take a look at the chart below, and if your interested in reading the “Is Nutrient Timing Dead?” from Precision Nutrition http://www.precisionnutrition.com/nutrient-timing
If you have any questions on nutrient timing and are an endurance athlete feel free to ask us here at Precision Fitness.