1) what is meant by "non-provisional patent application?"
A patent application is a set of documents an inventor files with the patent office in the hopes of obtaining a patent. There are "provisional" patent applications" and "non-provisional" patent applications. It would be slightly less accurate, but probably also slightly clearer, to refer to a provisional patent application as an "informal" patent application and a non-provisional patent application as a "formal" patent application instead.
Filing a provisional application is a relatively inexpensive mechanism for an applicant to document their invention with their patent office, thereby "calling dibs" on their invention as of the date the provisional application is filed. The applicant then has one year to decide whether or not to formally pursue patent protection for their idea. If they decide they do not want to move forward, they do nothing and one year after filing, the provisional application expires and is never heard from again. If they decide they do want to move forward, they can file a non-provisional patent application that, if done right, can "claim priority" back to the filing date of the provisional application.
2) can a "non-provisional application" holder stop sales of a similar product?
No, a patent applicant does not yet have an issued patent and thus has no right to exclude anybody from doing anything.
Once a patent issues from an application, the patent applicant becomes the patentee and theoretically has the right to exclude others from making, using, selling, and/or importing into the United States, infringing products. (There's a whole separate topic on the distinction between a "similar" product and an "infringing" product.) (I say theoretically because a patent owner is not always entitled to an injunction, which would "stop sales" of an infringing product - but that is also better suited for a separate topic).
3) how do we know that a particular product can not be sold due to patent registration?
Sell the product. If no one sues you, you're fine.
Although that sounds sarcastic, unfortunately it's closer to the truth than not. If you're contemplating selling a product and you're worried about patents in general or a patent in particular, you can obtain an "opinion of counsel" letter from an attorney that, hopefully, gives you a good faith basis for believing your product does not infringe the claims of a valid patent. The letter won't stop you from being sued or, if your product is found to be infringing, being liable for damages, but it should help prevent you from being penalized for "willful" patent infringement.