What is an Offer?
To form a contract, there must be an offer by one party, an acceptance by another party, and an exchange of consideration (something of value). The person who proposes the terms of an agreement makes an offer, and is called an "offeror" in contract law. The person to whom the offer is made is known as the "offeree."
The purpose of a contract could be the sale of goods, a pledge to refrain from a particular activity, or a promise to perform a task.
Example: If Sharon needs her house painted, she could ask a painter to complete the job for a set amount of money. The painter could either accept by stating, "Yes, I will paint your house for that amount," or simply by painting Sharon's house.
How would the painter in this example know how to accept Sharon's offer? They would have to look at the terms.
Terms of an Agreement
The terms of a proposed agreement must include enough detail for a person to accept and perform the task or obligation. Generally, and in particular with respect to consumer and commercial transactions, this means that certain material terms must be present in the offer. Material terms typically include the price and the subject of the contract, such as goods or services rendered. Depending on the subject of the contract, the quantity of goods and timeframe for delivery may also be considered material terms.
Terms may also include whether a person can accept through promise or performance.
The consideration is the value bargained for by the parties.
Example: Tom offers Dan $10,000 to build a fence. Dan accepts, and halfway through the construction process, Tom offers Dan another $5,000 to be paid upon completion. There is no enforceable contract for the extra $5,000. Under the original contract, Dan was already obligated to complete the fence for $10,000. The extra compensation is not supported by any new consideration (from Dan).
On the other hand, if Tom offered Dan an extra $5,000 for completing the fence one month ahead of schedule, there would be consideration for the contract to be modified (the speedy construction).
Last, but not least, a person must have legal authority to either make or accept a binding offer. This authority is called "capacity." Generally, a person is presumed to have capacity to make a contract if she is at least 18 years old, and of sound mind.