Unlike isolation exercises that requires heavy exercise equipment at the gym, circuit training can be done with or without any exercise equipment. Circuit training is circuit based workout focusing on core stability and functional strength which may not target and focus the specific area of the muscle group that you want to grow. However since it use whole muscles on our body, it can improve the efficiency of muscle activity, and calorie use.
Also because it requires to do variety of different exercise in a short time, it can give you the high intensity comprehensive workout routine for any circumstances.
Simply you just have to choose which part of your body you will train,(Total-body, Upper-body, Lower-body, Core & Trunk etc.) then choose 5~7 different exercises for that each body part. Compound all those workouts and treat them as an one set of exercises.
Let say you have choose push ups, dumbell shoulder press, dumbell row, squat and lunge to develop muscles in chest, shoulder, back, and legs. Doing exercise 10 repetition each, without a break, is a completion of an one round or one circuit, then repeating the round or circuit 2~3 times is what people call a circuit training.