Answer: When compost is finished, it is completely broken down and the original ingredients are no longer identifiable. I suppose you could store it until you want to use it, although as long as it does not contain fresh manure I don't see why you would need to wait. (The reason to wait in that case is fresh manure can contain pathogens you would not want near the vegetables you are going to possibly eat raw. It would be fine for an ornamental garden.) To hold it, take it out of the composter and pile it up, then cover it loosely with a tarp to prevent rain from leaching the nutrients out of it. You would not want to enclose it completely in an airtight situation because this could cause anaerobic conditions to develop.
Another approach is to run several batches simultaneously -- one batch of material being accumulated, one batch "cooking" and one batch this is essentially finished. Some gardeners use separate bins or piles or compartments for each, it depends on your personal preference and what works best for you.
Here are some instructions for using different methods of composting to help you get an idea of the different ways it can be handled.
I hope this answers your question!
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