Term life insurance provides protection for a specific period of time, the "term" and is designed for temporary circumstances. It makes the most sense when your need for coverage will disappear at some point, such as wehn your children graduate from college or when a debt is paid off.
The most common term policies provide coverage for 20 years, but they can run the gamut from one-year polocies to terms of 30 years or even longer. In some cases, a term policy may also be converted to a permanent policy. Typically, term insurance offers the greatest amount of coverage for the lowest initial premium and is a good choice for youung familites on a tight budget.