In the US it technically varies state to state though most states are now "at will", you can leave at any time (you can just walk out one day and never return and that's legal though rude) and the two weeks is just a common courtesy.

The flip side of this is the company can fire or lay you off at anytime. So while 2 weeks notice may not seem like a lot, the system we have here is actually potentially much harsher for employees than employers.

As with the 2 week notice courtesy from employees to employers, most places will offer some sort of severance pay to soften the blow, entice employees to sign an NDA and smooth over any legal challenges that might pop up despite the "at will" employment situation.

In ths US, as far as I know in most places, two weeks is a courtesy, not a requirement (unless you have some kind of contract that says otherwise). You can tell your boss "I quit" and walk out and never return and it's perfectly legal (though probably not wise, depending on circumstances).

I don't believe it's at-will employment though in the UK.

You have to give a month's notice because your employer can't arbitrarily show up at your desk, say pack up your stuff and get out of the building within the hour (with security hovering around you and your computer locked down) and this is the last day we're paying you for.

Here in Sweden it's usually three months for any long time employment. One month for short term.

Reading about zero or two weeks notice here makes me thinking what that does for the job market. On the one hand it surely makes for more movement, on the other hand it must make for a more ruthless job market. One of the upsides that I perceive with the three months notice is that it makes you think long and well about quitting, and encourages you to work things out. You don't just rage quit, because you'll have some three uncomfortable months.

If however, things really don't work out and both parts acknowledges this, you often come to an agreement of parting earlier.

Exactly what does the "minimum" mean here? I always wondered that. If you just walk out the door without saying anything and don't come back, what will they do? Are the police going to come drag you out of your home and force you to sit at a desk? Do you get fined or something? I'm pretty sure that, everywhere I've worked, you're free to do that if you want to, and there aren't really any consequences besides your now-former employer being unhappy with you, along with any other potential employers that find out.

If you don't stay for the minimum number of days that you have to as an advance notice, I'd say that (if the UK is similar to other EU countries) you'd have to compensate your employer for that. And that would mean something like paying them what they would have paid you for the number of days that you missed, plus any damages resulting from those missing days.

This enforced by law, so if you don't pay, they would just throw you in court.