What do strong nuclear force and weak nuclear force act on?

The strong force acts to overcome the extreme electric repulsion that exists within the nucleus and make it a stable configuration (in most cases). It is very short range, and so is not experienced outside the nucleus. In the case of the strong force, there is an exchange particle called a gluon that acts only on particles made of quarks that have the property called color charge, which has nothing to do with the familiar notion of color). This includes both protons and neutrons.

The weak force is more "universal," acting on quarks and quark-derived particles as well as the while family of leptons, comprising electrons, muons, taus, and their neutrinos. It is generated by the exchange of what are called "intermediate vector bosons," which modifies the flavor of the quarks, allowing a down quark to become an up quark and a neutron to become a proton (a process known as beta decay).

The strong nuclear force acts on protons and neutrons within an atomic nucleus, binding them together. The weak nuclear force is responsible for processes such as beta decay and neutrino interactions within the nucleus.