Force
It is a push or pull on an object.
Force comes about when there is an interaction between two objects. A force can only take place when there is some sort of interaction.
There are times when there are more than 2 forces taking place on an object.
Let us explain;
Scenario 1
A glass of water placed on a table may look like nothing is happening to it which is wrong. First the force of gravity keeps the glass of water grounded on the table. The movement of water molecules in the glass. There will also be small forces trying to push the glass when the wind blows against it. There is also an upward push from the table supporting the glass.
Scenario 2
When you are throwing a ball up in the air there are several forces occurring at the same time. The ball experiences gravity forcing it to drop back down. Friction against the wind as it goes up. The force you release when you throw/push it.