An offer is an essential element required to make a valid contract. Please outline and explain in your own works what an offer is.

An offer is an essential element required to make a valid contract. Please outline and explain in your own works what an offer is. Please include in your explanation all matters related to the concept of an offer, such as the ways in which an offer may be made, the duration of offers, and matters that may appear to be an offer but do not amount to an offer