won't crank

poor ignition contacts, faulty starter solenoid, battery lead grounding out somewhere, Foreign object in flywheel housing, cylinder , sticking brushes in starter........

The list could go on and on. More information is required.

With your headlights on, Ignition in start position; headlights bright or dim? Does the engine turn by hand?

What do you mean when you write "everything just quit" Nothing electrical at all? All electrical but no cranking?

You see where we're going with this. I'm also assuming that we can rule out an engine immobilizer? One never knows...