In most offices, the support staff type employees (i.e., secretaries, file clerks), typically work 8 am to 5 pm or 8 am to 6 pm. In places like factories, where it's shift work and paid hourly, there are three 8 hour shifts a day. Sometimes you can get overtime pay to cover a second shift, but generally that's it, you put in your 8 hours (with one 1 h break for lunch/dinner/coffee - not sure what meal third shift breaks for), and go home.
For salaried employees (those who get paid a fixed amount, no matter how many hours are being worked), it's more that you get paid for a certain job that needs to be accomplished. There are some people who get salaries who do have minimum and maximum hours defined in contracts, and often don't stay to work extra hours. For example, a lot of our lab technicians fall into this category. They show up at 8 a.m. and leave around 5 or 6. Whether or not they stop for lunch, sometimes they just grab a 15 min break for a sandwich, is up to them generally. Those are their normal hours, but they have some flexibility too. If they need to stay late one day assisting with an experiment, they can come in late or leave early another day to make up for it. Or, if someone needs to stay home on a weekday waiting for a repair person, or something like that, then they can come in and get whatever needs to be done on a Saturday instead, or work late several days the next week. The idea is you have a guaranteed paycheck coming to you, and aren't penalized for the slow weeks, but then don't get anything extra for the busy weeks. Hopefully it pretty much evens out.
Then there's the last category, those of us who are salaried and don't get any extra pay for working 60 to 80 hour weeks. Often, the salaries are higher to start. But, the reason you work those hours is more that you have a personal stake in keeping the office/company/lab running. For example, in a law firm, the secretaries and paralegals may work pretty fixed hours, while the associates who want to make partner someday work their butts off; the idea is if they can bring in enough clients and enough money to the firm, they'll be rewarded with a partnership in the firm.
Having grown up in the American culture, that's just normal to me. If you want more, you work harder for it. I have a hard time really understanding how people elsewhere can get anything done with so many holidays and breaks, etc.