Erwin Schrodinger, in 1926, published his equation, which famously became known as the "Schrodinger equation." This is building on the work of de Broglie (who inspired Schrodinger) on wave-particle duality. Schrodinger proposes that you can actually know the wavefunction of a particle. The wavefunction is the distribution of the particle's energy in space. The wavefunction is the solution to the Schrodinger equation and contains all of the information about a quantum system that can be known.
The wavefunction is not a directly observable quantity. The wavefunction is an abstract mathematical entity. However, physically meaningful information can be deduced from the wavefunction. The square of the wavefunction is known as the probability density. The probability density is a measurable value and it can be used to measure the probability of locating an electron at a specific point in space.