Calling a function on a table, and how does this code work?

function module:GetDatabase(sheet)
	local database = {}
	function database:PostAsync(key, value)
		return doPost(sheet, key, value)
	end
	function database:GetAsync(key)
		return doGet(sheet, key)
	end
	return database
end

So, from my understanding, whenever PostAsync() is called, doPost is returned, and whenever GetAsync() is called, doGet is returned? Am I correct in this understanding?

Also, functions are being called on the table? This code is confusing me for some reason.