In order to successfully sell your product on Amazon, you need...sales. Duh.
But in order to get sales, your product must be put in front of the right customers who are searching for exactly what you have to offer.
Then, and only then, when the customer sees your product, determines that you are going to provide them exactly what they were looking for, will you get a sales conversion.
With every sales conversion you get, you are one step closer to convincing the A9 Algorithm (the enormously super secret artificial intelligence system that runs the entire Amazon.com platform) that you are worthy of being higher up in the search results.
IF your sales continue day after day, and you build momentum (a favorite snack desert of the A9), then the A9 rewards you with even higher rankings. With higher rankings comes more customer eyeballs on your product, which comes with more sales, and more ranking, and and and.....
Until you reach Top of the Search.