If someone holds a knife to your throat and says 'give me your money or I'll kill you', they are using force because you don't have a choice of whether to deal with them. You still have a choice (whether to pay up or die), but you don't have the choice of removing yourself from the situation - they are forcing the choice on you.
Likewise running over someone in your car is using force - they don't have the choice of being somewhere else at that time.
It is useful to classify force as one of three types:
Force is a favorite word of the politically correct which they misuse to make themselves appear to be victims.
People often use phrases like 'I was forced to buy the chocolate' or 'I was forced to take this course'. This is unlikely. They probably had the option of just leaving the store, or walking past the chocolate display or even getting a job.
Sometimes people say 'I was forced to make that choice'. This is only true if someone (or some thing) threatened force if any other choice was made.
Clearly when people make agreements or contracts with each other they put themselves in situations in which force can be used to ensure compliance. If they entered into the contract freely, then they have consented to that action. In this case they are not victims.