Both protons and neutrons are found in the nucleus of an atom. The third type of particle that an atom has, electrons, are found in orbitals outside of the nucleus.
The nucleus is the densest part of an atom. Both neutrons and protons have significant mass, while electrons are virtually massless. This model was discovered as a result of the gold foil experiment in 1911 by Ernest Rutherford. Neutrons have no charge, while a proton has a charge of +1. Similarly, electrons have a charge of -1. Each atom has an overall charge that can be determined by subtracting the amount of electrons from protons.