Endgame Progression
From Destiny 1 Wiki
After reaching level 20, players will no longer gain experience toward leveling their subclasses. Players will instead gain experience towards their Mote of Light. The player's experience bar is replaced by a Mote of Light bar. When the bar fills up, the player gains 1 Mote of Light. Mote of Light allows the player to level beyond the soft level cap of 20. It allows can be used to purchase and upgrade gear from The Speaker in The Tower.