Indicates a deadline or time limit by which an action must be completed. Used with verbs expressing completion or punctual actions.
Please submit the report by tomorrow.
Please submit the report by tomorrow.
Please come here by 5 o'clock.
I left early so I would make it in time for the 9 o'clock meeting.
We have to decide by next Friday.
まで shows a continuous extent up to a point in time or space (e.g. 5時まで待つ = wait until 5:00), while までに marks a deadline by which a single action must be completed (e.g. 5時までに来る = come by 5:00).
before now; so far; until now
Combination of the particle まで ('until') and the particle に, forming an adverbial expression meaning 'by (a certain time)'.