I've seen a lot of people praising the sound design concept for a film but what exactly does that mean, and can you give an example?
When I establish, or experience, sound design based on a concept, that usually means a set of overarching design principles or themes that act as a set of heuristics that can guide decisions - and critiques - made along the way. Is it intended to compliment or contrast the emotional tone of a scene? Are there emotive descriptors that can be used to influence the piece? Are there textural elements for certain scenes, actions, or characters? It's rare that there is just one concept (unless it boils down to "hyperreal," "uncomfortable focus," " distance", or "uneasy"), but rather a small set of easy-to-remember strategic principles that frame the creative challenge before you and guide more tactical decisions.
This approach not only is helpful in the making of things, but also a key way to frame challenges, hold meaningful critiques, establish shared language between collaborators in discussing audio decisions, and defend aesthetic decisions beyond "I did it because it sounded good:" That, in my opinion, should always be the result, but never a justification.
Likely referring the aesthetic, and how that supports (positively) the underlying story/visual, and it's extreme uniqueness of style (like the sound palette of Transformers or The Matrix, for instance) - round an subtle for a drama, or abrasive and agitated for some hyperreal action piece like 300 or Sin City, or smooth and punchy like Inception, harsh and frightening for a thriller/slasher, etc.
So many aesthetic styles that can be chosen, and finding that best match to drive the story and thus serve the story's intent productively.
Overall that's my best guess.