1. Gravitational Force: This is the force of attraction between any two objects with mass. It's what keeps us on the ground and what causes the planets to orbit the sun.

2. Electromagnetic Force: This force involves interactions between electrically charged particles. It's responsible for everything from holding atoms together to generating electricity and magnetism.

3. Strong Nuclear Force: This extremely powerful force holds the protons and neutrons together within the nucleus of an atom. It's responsible for the stability of matter.

4. Weak Nuclear Force: This force is responsible for radioactive decay, where atomic nuclei transform into other elements.

These four forces are fundamental to understanding how the universe works, from the smallest particles to the largest galaxies.