Bodyweight training is a resistance exercise that uses no added external weight. Examples would be press ups, pull ups, squats or tricep dips.
Bodyweight training is great for improving muscular endurance, which is your bodies ability to repeatedly contract your muscles. This type of training is also the one most closely associated with creating muscle tone, as it improves the shape of the muscles without increasing the size.
Bodyweight training can also be a great way to lose weight, as it raises your heart rate, challenges your muscles and increases your metabolism.
To get the most out of your workouts try to perform circuits, which is when you perform exercises straight after one another. You would then rest for a minute or two and then repeat the circuit. How many circuits you do is up to you and should be determined by your fitness level.