Level term: the death benefit stays the same. The premium may stay level for the whole term (10-, 20- or 30-year level-premium term, with a guaranteed or non-guaranteed premium), or it may go up every year (annually renewable term, ART). Indeterminate premium: the insurer charges a current premium below a guaranteed maximum and can change it.
Decreasing term: the death benefit shrinks over the term while the premium usually stays level. It fits a debt that is being paid down: mortgage redemption (mortgage protection) insurance and credit life.
Increasing term: the death benefit grows, for example to keep up with inflation. It is usually sold as a rider, such as a cost-of-living or return-of-premium rider.
Also on the outline: universal life designed to work like term, such as guaranteed universal life (GUL) and survivorship GUL, which provide a guaranteed death benefit with little cash value.