The difference between them is that they affect different particles. The electromagnetic force is the one most familiar to us. It affects electromagnetically charged particles like protons and electrons. The particle that carries this electromagnetic force is the photon. The strong force affects quarks.
Quarks have a property called colour charge that attracts one quark to another.
It is analogous to electromagnetic charge in that it attracts one quark to another. The charge carrier is the gluon . The strong force only affects the colour charge of the quark. It does not affect flavour. The final force is the weak force and this the most weird.