Understanding Index Options: Call vs. Put Understanding Index Options: Call vs. Put Index options are financial instruments that give investors the right, but not the obligation, to buy or sell an underlying stock index at a predetermined price before the option expires. DSIJ Intelligence-1 / Thursday, January 30, 2025 / Article rating: 5.0 Index options are financial instruments that give investors the right, but not the obligation, to buy or sell an underlying stock index at a predetermined price before the option expires.