The producer of a block collects a subsidy of freshly created coins and the fees attached to the transactions they included. Together these fund network security: they are the reason miners buy hardware or validators lock capital.
Rewards are the supply side of the market. Every block issues coins that eventually reach exchanges, so the reward schedule tells you the structural sell pressure a chain carries.
Example: a subsidy of 3.125 coins every ten minutes is 450 coins a day. At a $60,000 price that is $27m of new supply per day that the market must absorb, before counting fees. When the subsidy halves, that figure halves too, which is the mechanical story behind halving narratives.
Related: proof-of-work, halving