An estimate is basically a ‘guesstimate’ or rough, educated guess based on what a job MAY cost.
An estimate is an informal idea of price based on limited information.
Consider it a starting point in terms of costs, which can go up (or down).
Estimates CANNOT be used as a legal standpoint for price.
On the other hand, quotes are presented formally and represent a contract between you and the customer.
As such they can be used as legal standpoints for price should a dispute arise.