There are four fundamental forces which govern the universe which must be understood to more deeply appreciate astronomy.

Gravity is the weakest of the four forces, yet its range is infinite and it is the most dominant force in governing the shape of the universe.  Gravity on the earth is weak enough to allow you to jump off the ground, yet the gravity of larger bodies is strong enough to bend light.  For example, Einstein predicted that light along a gravity well would follow a longer path than that outside of one.  This has been demonstrated to be true, as experiments with the Voyager spacecraft when it was near the sun have shown.

The electromagnetic force includes both magnetism and electricity, which at the fundamental level are the same expressions involving an exchange of photons (which are quantums of light or electromagnetic radiation).  The range of the electromagnetic force is infinite due to the zero resting mass of a photon.  This force holds atoms together as well, as it is electromagnetism that binds negatively charged electrons to positively charged nuclei.  Light, radio waves, x-rays and microwaves are all travelling electromagnetic waves and differ only in wavelength.

The strong force is by far the strongest of the four fundamental forces.  It has an extremely short range, yet it is powerful enough to hold the nuclei of atoms together against the enormous forces of repulsion of their protons.  There is yet a more refined force of which the strong force is said to be the residue of and that is the color force, which binds the constituents of each proton and neutron together.

The weak force governs the movement of atomic elements within the atom itself, for example, during atomic decay.  Like the strong force it's range is extremely short and operates only on the atomic level.  It is essential to the life of stars, however, as recall that the first stage of hydrogen-helium fusion is the movement from hydrogen to heavy hyrdrogen (deuterium).  It is the weak force which governs a hydrogen atom to take on a neutron to become deuterium during the fusion to helium.