When mingling at a party (or bash), I try to avoid talking about macronutrients. Despite my obvious passion for the subject, chances are people's eyes would glaze over (though they still would prefer it to me talking about cats). Yet you already know a fair amount about macronutrients: carbohydrates ("carbs"), protein, and fat. These help define the types of foods we eat to provide energy for the body.
There are other purposes for macronutrients, such as providing the necessary components for body growth and repair, but the primary purpose of proteins, fats, and carbohydrates (especially fats and carbs) is to provide energy. Energy for the body is measured in calories. While vitamins and minerals (micronutrients) are required in small quantities, macronutrients are needed in large supplies. Our bodies use lots of energy every day (even when we're not particularly active) and we get that energy from food.
When hitting the road (not literally, of course), it's always a good idea to plan ahead to take advantage of the activity opportunities of your destination. For example, many hotels have fitness centers (of widely varying quality), a beach trip can feature lots of water activities (swimming, snorkeling, bodyboarding, wind surfing, etc.), and a trip to the San Francisco Bay Area can (and should) include hiking and biking and, of course, 
