An excellent definition of what a market is comes from ThoughtCo (2019): A market is any place where sellers of particular goods or services can meet with buyers of those goods and services. It creates the potential for a transaction to take place. The buyers must have something they can offer in exchange for the product to create a successful transaction.
The market will judge your idea one way or another... why not hear the verdict BEFORE you quit your day job? This video will go over how to conduct basic market research to make sure your idea is worth the effort (and the investment).