Premium-Paying Term is the duration over which premiums are due. In a regular-premium endowment, PPT equals the Policy Term. In a limited-pay or single-pay plan, PPT is shorter — you finish paying early but the policy keeps running and accruing bonuses until maturity.
LIC Jeevan Labh offers PPT options of 10, 15, or 16 years against policy terms of 16, 21, or 25 years respectively. The shorter the PPT, the higher the per-year premium but the better the implicit XIRR (because your money compounds inside the policy for longer after you stop paying).