Explain a Confusing Film Ending in Plain Terms

The credits rolled and you are still not sure what happened. This walks through what actually occurred on screen, what it means for the characters, and the two or three genuine interpretations of anything left deliberately vague, in plain terms.

Explain the ending of [film title] in plain terms. Walk through what actually happened on screen first, then what it means for the characters, then note any deliberately ambiguous parts and the two or three most common interpretations, without turning this into a full essay. Assume I have already watched the film and do not need the earlier plot recapped in detail.