A virtual particle is a concept in quantum physics that describes temporary fluctuations in energy that occur in empty space. These particles are not directly observable but can influence real particles and forces. They appear and disappear in extremely short time frames, consistent with the uncertainty principle, which allows for brief violations of energy conservation. Virtual particles are often associated with interactions between particles, such as in the case of the electromagnetic force mediated by photons. They play a crucial role in quantum field theory, helping to explain phenomena like Hawking radiation and the behavior of particles in quantum mechanics.