Word
Deploy
To deploy is to put your app somewhere that stays running, so it keeps working when your own computer is closed.
Also called: ship, go live, put it online
While you are building, the app exists only on your machine, and only while you leave it running. Deploying copies it to a computer somebody else keeps switched on, so it can do its work on a schedule and be reached from your phone.
Nothing about the code changes. What changes is who can reach it and what a failure costs: a broken app on your desk is a bad afternoon, a broken app your customers touch is a different category of problem.
The usual mistake is deploying before deciding what happens when it fails at three in the morning.