Forces are the means by which objects in the world influence one another.
If there were no forces then all fundamental particles would move about independently of each other so there would be no structures or communication at all.
There are 4 known types of forces in nature:
- Gravity - 1 type, always attracts.
- Electromagnetism - 2 types (+ and -) opposites attract, like repels.
- Weak Nuclear
- Strong Nuclear - 3 types (red green and blue)
Physicists are trying to explain these in terms of a single uniting force.