Weights are not necessary to perform an effective squat. Squats performed without weights are also known as "body weight squats" and are meant to be done without any additional equipment.
Squats are one of the most effective exercises, especially when trying to build muscle strength. They come in many varieties and work out the quadriceps, hamstrings and gluteals simultaneously. Body weight squats are particularly good for beginners looking to build up their endurance and strength. Performing body weight squats teaches those who are new to exercise how to use good form, which is essential in strength training. Because they don't require any exercise equipment, they can be performed at home or in the gym.