Index Survival Benefit
Imagine that you tell your child that you will give her a jar full of candy if she can do her homework ten days in a row! You may choose to give her the candy every 2nd or 4th day to ensure continued good behaviour or you may choose to give her a big reward after 10 days!
Similarly, some specific endowment plans and money-back plans are like scenario one. They pay out survival benefits on surviving for a pre-defined period, at specific points in the term of the policy - unlike the maturity benefit, which gets paid out after the policy term.