Deployment Main Settings
When ever you have to deploy the code from sandbox to prod you have to first make a connection between them for that you have to create first sandbox org and do all the requirement and then go the setup>>sandboxes>>create new sandbox
whenever the connection is done it will give a green double sided arrow
means your connection was successfully created and you can just move the functions from sandbox to the prod.
for successful connection between sandbox and the prod you have to select the Allow inbound changes ? and then your connection happens.