A particle accelerator is a scientific device used to accelerate particles, such as protons or electrons, to extremely high speeds. These particles are then collided with a target or other accelerated particles, creating high-energy conditions that mimic the early universe or other natural phenomena. The discoveries made with particle accelerators have led to breakthroughs in various fields, including the discovery of the Higgs boson in the Large Hadron Collider, contributing to our understanding of fundamental particles and the laws of physics.