And then again...
We're in the dark here, without any response from the OP to indicate the context or purpose of his question, but thinking about it overnight (sad or what?) I suspect there are circumstances when we do need to differentiate between the different descriptions, and those arise whenever we try to answer the last question - ie why do writers do this?
The kind of build-up described in The Sixth Sense (which to some might be "foreshadowing") doesn't really require an answer to the 'why'. This is basic plot mechanics, making sure your 'pay-off' has been 'set-up'. The writer has no choice but to do this, there's no 'why' involved at all - if we don't set up a plot twist and it comes out of nowhere in total contradiction to everything that's preceded it, that's just 'cheating' and thoroughly bad writing. Put it this way - would TSS work if the MC had been audible to other characters? No - it would be a very bad story that didn't make sense.
The build-up in The Shawshank Redemption is different, because it's used for the purpose of intrigue. Plot-seeding (like The Sixth Sense) deliberately tries to disguise itself from the reader because you don't want them to guess the twist before you play it. Foreshadowing is stuff you do want the reader to spot, because it enhances his enjoyment. TSR doesn't blow the plot, it's cleverly hidden so as not to spoil what the pay-off is going to be, but it's out there, and you're expected to notice. The reader/viewer should be asking why are we seeing this, what's he up to, what's going on? Intrigue is one of the best ways to sustain narrative drive - it keep the reader turning pages to find out what it's all about. That's why we do it...
Similar to intrigue is the use of foreshadowing to create suspense. Give a reader a clue as to what might happen later, and they're on the edge of their seats waiting for it to happen. Again, enhanced narrative drive.
The simplest, plonkiest form of foreshadowing is just to keep bums on seats. You're in the middle of a gentle character-development section of writing, and there's a risk your less patient readers will ditch the book and go to the pub instead. So you drop a hint. You try as subtly as you can to say 'stick with it just stick with it, something really great is going to happen in a minute'. Relatively inexperienced writers will plonk this out in chunks of 'Little did they know this was a big mistake' (pause for vomiting) but even that can be done well, as Chandler proved repeatedly. Phrases like 'As soon as she walked in I knew she was trouble', or 'I should have run a hundred miles before I opened that door' may be crass out of context, but they don't half keep readers in their seats wanting to know what happened next. They're best used as chapter hooks or end of section seques, but the fact is they work. In my opinion, the subtler the better - I'd rather just have a description that gives me an indefinable sense of unease than be told directly I need to feel uneasy - but they work and they sell books.
And in the end, that's why we do it. That's why we do most things. We want the reader to enjoy the read, so we need to thread that little string through the ring on his nose and lead him very gently alllllll the way...
Louise