I uh… USians don’t do those. When they do, it tends to be a one-sided kind of thing to protect the company’s interests—NDAs, codes of conduct, accept our policies today and whatever we change them to in the future, that sort of thing.
Most places, work happens at the whim of the employer (and, for what little it’s worth, the whim of the employee): employment is “at-will,” states are “right-to-work,” and so on.
Don’t know about others, but I’ve never once in my life signed a contract to work in the US.
Your monetary compensation is in an offer letter you sign to accept the role. Salary exempt status is a fixed value per time period, or separately a hourly rate.
If paid hourly, you're typically entitled to 1.5x pay after 40 hours of work. Salaried exempt status are not mandated overtime pay.
What hours you work depends. Salaried is expecting a job to be done regardless of the hours to complete. Hourly is a mixed bag of "the schedule for next week is posted every Tuesday" (common in restaurants) or routine hours long-term (such as shift work in factories).
Most tech positions don't have fixed work hours, beyond what's required by the law. The salary, position, benefits, etc. are the part of employment offer that you do sign, and there are employment handbooks etc. that you also acknowledge when you onboard, but from the company side the offer is usually the only document they sign.
You don't sign a contract buying something in the supermarket, yet a contract is still formed. You negotiated or discussed with the employer about pay and responsibilities, of course they are part of any such contract and their option is to dismiss you, not unilaterally change the terms.
