There are different forms of exercising. Weightlifting is when you lift weights in order to build muscle. Muscle gain is popular in order to bulk up. Cardio is a type of exercising that gets the heart rate up. Many people will do cardio exercising in order to get healthy. However, some people will put several workouts together because they have more than one goal to achieve while working out.
There are variety of times that people do cardio in relation to their weightlifting. Some people do it before their weightlifting activity and some do it after. It just depends. It all depends on what you are trying to achieve. It also depends on your stamina. If you have trouble with your stamina, then you might not want to do both of these one after the other.