A proton is a positively charged subatomic particle found in the nucleus of an atom. It plays a crucial role in determining the atomic number of an element, which defines the element's identity. Protons, along with neutrons, make up the atomic nucleus, while electrons orbit around it. Protons are essential for the stability of atoms and are involved in various nuclear reactions. They are one of the fundamental building blocks of matter, and their interactions are governed by the strong nuclear force. Understanding protons is vital for fields such as chemistry and particle physics.