Term insurance is basic, inexpensive and easy to understand. It gives you all the coverage you need and none that you don't. That's why it's the best choice for almost everyone.
As the name implies, a term insurance policy is good for a specific period of time; that can be one year, 10 years, 20 years or even up to 30 years. Given that you generally need life insurance only until you've managed to save up money elsewhere, just pick the term that dovetails with the time you need coverage. If you die during that term, your beneficiaries get a payout, known as the death benefit. If you die after the term expires, there's no payout.
Term policies typically have maximum issue ages. If you're past age 80, you'll have a hard time getting term insurance. (You almost certainly won't need it at that age anyway.)