If you only do these 6 exercises, you will train your entire body!
The squat is the king of lower body exercises. This movement will train the quadriceps, adductors, glutes, hamstrings, lower back / spinal erectors, and core.
The deadlift trains more muscle groups than any other exercise that we know of. It trains the posterior chain which includes hamstrings, glutes, and spinal erectors
It trains the chest, the anterior shoulders, the triceps, and muscles in the lower body if done correctly.
The overhead press trains the shoulders, the triceps, the core, and several other stabilizer muscles in the upper body.