A release is a signed document that authorizes material or products to be shipped or picked up (often by a third party).
For example, I own 40,000 lbs. of steel that is currently stored in a public warehouse. I want to send in a truck to pick the steel up. The warehouse won't load it onto the truck until I provide a signed release form authorizing them to allow the truck to remove my steel.
A release schedule is pre-arranged agreement to have X amount of goods or product ready for shipment on a regular basis. I might inform the steel mill to have one truckload of steel packaged and ready to ship by the 15th of each month. That would be my "release schedule."
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