Heisenberg Uncertainty Principle

The Heisenberg Uncertainty Principle is a fundamental states that for any given quantum particle with position $x$ and momentum $p$, then the product of the standard deviations of the measurements of $x$ and $p$ must be of the order of Planck's constant ($\hbar$), which is a non-zero, positive-valued, real number.

Mathematically it is represented with this equation: $\left(\Delta x\Delta p\geq {\frac {\hbar }{2}}\right)$.

In English, this means - for example - that if we measure the position of the particle perfectly then there has to be a non-zero error in our measurement of momentum (and similarly the reverse) and so we can never know the exact position and momentum of a particle at any instant.