Quantum physics is just the physics of the incredibly small. Quantum physics tries to explain the behavior of particles like electrons, protons, and neutrons. Quantum physics even describes the particles which make up these particles. The difference between quantum physics and normal physics is that the common laws of physics begin to deteriorate on small scales.
Quantum physics involves trying to quantify/measure the small bits of the world...atoms, electrons etc. The problem arises when you try to locate something this small...you use an electron to measure an electron...so it hits it and it automatically changes the picture that you're trying to take. So you have to "predict" what will happen rather than actually measure it.