What is an estimate?
An estimate is a planning document that shares your best guess of the cost before the work or delivery begins. It records when it was prepared and usually notes when the numbers should be reviewed again, so both sides understand the schedule and the room for changes.
For example, if John Hotdogs is asked on March 2 to cater an office lunch on March 6, he can send an estimate dated March 2 that lists the expected $120 cost and mentions it will be refreshed once the final headcount arrives on March 4. Those dates tell Clara when to confirm details and let John adjust the plan if something changes.