Maturity Benefit is the payout received when the policy completes its term and the life insured is alive. For a participating endowment, it equals the Sum Assured + Vested Bonus + Final Additional Bonus (if applicable). For non-participating plans, it's the Sum Assured + any guaranteed additions.
Maturity proceeds from a life insurance policy are tax-free under §10(10D) provided the 10× SA rule is met (for policies issued after 1 April 2012). They are paid as a lump sum unless you've opted for an annuity or settlement option.