Sometimes, if you leave something like chips out in the open, it catches moisture from the air and is not as crisp after that.
Is the food good to consume even after that?
Chips become soft after leaving out, but that doesn't necessarily mean they've gone bad. If you leave them out long enough they will, or they might get contaminated with things, but things which have just gone soft are probably fine - although whether you'd want to eat them or not is a different matter, because I've done it and they're not very pleasant.
However, if in doubt about the safety of any food, don't eat it. Food poisoning is not nice.
There's different things here -- loss of texture/freshness (ie, stale), and unsafe to eat (spoiled)
There's lots of things out there that aren't unsafe to eat, but you might not want to -- eg, the brownies that have become so hard that you might be worried about chipping a tooth.
Some things can be saved after they've had issues -- it's possible to reheat corn chips or deep fryer to crisp them back up. Limp carrots will come back if wrapped in a damp towel and left in your crisper for a day or two. Limp lettuce might revive in an icewater bath. Day-old bread (slightly stale, not rock hard) can be put in a dampened paper bag and put in the oven on low heat to revive.
... but all of these assume loss of freshness, not rotted / covered in mold / etc. If it smells funny, there are bugs crawling all over it, it's now fuzzy, or it's taken on new interesting colors ... it's time for the compost or trash.
Sometimes, slightly less than fresh item are great in other things -- vegetables past their prime can go into making stocks; stale bread for croutons, french toast or bread puddings.