The need for and the existence of contracts seems to have grown in recent decades. Back in the old days, there were few written business contracts, and many business and personal deals were done with a handshake.
In addition to being clear and specific, a contract must meet certain criteria to make it legally enforceable. A legally enforceable contract can be used in court to support a decision on a disputed item. If a contract does not have certain essential ingredients, it is not legally enforceable.
Most contracts never see a courtroom and they could easily be verbal unless there is a specific reason for the contract to be in writing. When something goes wrong, a written contract protects both parties. If one party to a valid (enforceable) contract believes the other party has broken the contract (the legal term is breached) the party being harmed can bring a lawsuit against the party who it believes has breached the contract.
The legal process, or litigation, determines whether the contract has been breached or whether there are circumstances that negate the breach. The court, however, will only hear a contract dispute if the contract is valid.
Many people use the terms contract and agreement interchangeably, but they are not precisely the same thing. Black's Law Dictionary defines an agreement as "a mutual understanding between...parties about their relative rights and responsibilities." It defines a contract as "An agreement between...parties creating obligations that are enforceable."
There are six required, essential elements for a contract to be valid (enforceable by a court). The first three, considered here together, relate to the agreement itself, and the other three relate to the parties making the contract.
As noted above, verbal contracts can have the force of law, but some types of contracts must be in writing, like long-term contracts and contracts for marriage (pre-nuptials). There is also such a thing as an implied contract. You can unknowingly enter into a contract with someone and be forced to abide by its terms.