The phenomenon you're referring to is known as quantum superposition. In quantum mechanics, particles such as electrons can exist in a superposition of multiple states simultaneously, meaning they can be in multiple places at the same time or possess multiple values for certain properties.
However, it's important to note that this does not mean that a particle is physically present in multiple locations simultaneously in the classical sense. Rather, the particle's quantum state is described by a mathematical function called a wave function or state vector, which encompasses all the possible states the particle can be in. These states are represented by probability amplitudes, and when squared, they give the probabilities of finding the particle in a specific state upon measurement.
According to the principle of wave-particle duality, particles can exhibit both wave-like and particle-like behavior. The wave-like aspect allows particles to be described by superposition, where they can be in multiple states at once. However, when a measurement is made to determine the particle's properties (e.g., position, momentum, or spin), the wave function "collapses" into a single state corresponding to the measurement outcome. This collapse is random, and the probability of obtaining a particular measurement outcome is given by the squared magnitude of the corresponding probability amplitude in the wave function.
An example often used to illustrate superposition is the famous thought experiment called Schrödinger's cat. In this hypothetical scenario, a cat is placed in a sealed box along with a device that, according to the laws of quantum mechanics, can be in a superposition of both activated and not activated states. Until the box is opened and an observation is made, the quantum state of the device is in a superposition, and thus the cat would be considered to be in a superposition of both alive and dead states. However, upon observation, the wave function would collapse, and the cat would be found in either a definite alive or dead state.
It's important to highlight that quantum superposition is a fundamental aspect of quantum mechanics, and it has been experimentally verified through numerous experiments, such as the famous double-slit experiment. However, the exact nature and interpretation of superposition, as well as the mechanism behind wave function collapse, continue to be subjects of debate and interpretation within the field of quantum mechanics.