Nuclear Physics is a field of physics, yes. It involves interactions between atomic nuclei. Nuclear fission, nuclear fusion, nuclear decay (though in some ways that is more particle physics).
Wikipedia gives you a good definition and a very large list of areas. There's also the "Simple English" wikipedia. They give a very short and good definition for Physics. See...
The main branches of classical physics include: Classical Mechanics Electromagnetism Optics Thermodynamics As well as many other sub-branches like hydrodynamics, aerodynamics, etc. In modern physics,...
Molecular physics looks at the subatomic world. It looks at particles such as quarks, Leptons and a major study by CERN in Europe is searching for a particle known as the higgs boson. These...