Quantum physics refers to the unusual concept of the probability wave.  What this means is that a particle - say for example an electron - when not being measured (located), takes the form of a field or wave of probable locations, some being more probable or likely than others.  So from one point of view the electron is a solid little energy particle located in a particular spot.  And from another point of view it is an energy field or wave-form of possible locations (the extent of the probability-wave is based on Plank's constant (a very tiny quantity) and defined according to Heisenberg's Uncertainty Principle).  This is the so-called wave-particle paradox in quantum physics; a particle is also a wave, a wave is also a particle.

On the macroscopic level of everyday objects, this effect is not noticeable (because the Plank Constant is so tiny).  On the quantum physical level however the effects are noticable.

Quantum physics