Protons are found in the nucleus of the atom and they are bounded together with neutrons. Along with neutrons, protons make up the vast majority of the mass of an atom; electrons, which orbit around the nucleus, are of negligible mass. Elements are defined by the number of protons that they have; thus, while a change in the number of electrons will change the charge of the atom, known as an ion (and a change in neutrons changed the weight, known as an isotope), a change in protons creates a whole new element (e.g., an atom with one proton is always hydrogen and an atom with two protons is always helium).
The force (known as the nuclear force) that hold protons and neutrons together in the nucleus are extremely strong, and it is not a bond that is easily created or destroyed in nature. The process of bringing protons together to form a new element is known as nuclear fusion; only the core of stars is known to be hot and dense enough for this to occur. Splitting a proton from other protons is known as nuclear fission, and this is the basis of nuclear bombs.
A proton is made up of three quarks and is classified as a baryon particle. Quarks are considered fundamental, and they come in six different types, as well as having their own spin and energy charges. Quarks were originally proposed by the physicist Murray Gell-Mann in 1964, and they are named after a nonsense word from the James Joyce novel "Finnegan's Wake."
Protons were discovered in 1909 by Ernest Rutherford during an experiment that is now known as proton scattering (or Rutherford scattering). Common belief at the time was that atoms were arranged like a flat manner (known as the plum pudding model). However, when Rutherford shot atoms through a narrow tube onto a gold sheet, there was a uniform distribution to the arrangement of the atoms on the sheet. Rutherford correctly deduced that this was because the atoms had a centralized mass, around which the electrons orbited. The term "proton" was coined by Rutherford in 1920.