What's the difference between "will not" and "will never"?
- He will not get in.
- He will never get in.
Can anyone explain to me which one of the above sentences is correct and why?
They are both grammatically correct, but they mean slightly different things.
He will not (or he won't) is simply a statement about the future. It's not specific about time or anything else, and is just the simplest possible way to make the statement. For example, it might be used in the following exchange:
"Yesterday we had to throw a man out of the bar. But if he comes back, he won't get in, because I hired a bouncer to watch the door."
Never makes a stronger statement, that something will not ever be true at any time, under any circumstances. Mostly it's used for emphasis. For example,
"Roberto is applying for membership in the Explorers' Club, but he will never get in, because last year he got drunk and insulted the president's mother."