What is the Strong Nuclear Force?

The Strong Nuclear Force keeps protons and neutrons together in the nucleus.Its range is no more than about 3-4 fentometres.
It has equal effects between a proton-neutron, neutron-neutron and proton-proton combinations. It is an attractive force from about 0.5fm to 3-4fm. At smaller separations than this it is repulsive so as to stop the nucleus collapsing in on itself