Both are "discount rates" in the sense that they turn future money into present value — but they answer different questions, and mixing them up leads to overvaluing risky businesses.
Risk-free rate. The return you could get with essentially no risk of loss — typically approximated by short-term government bond yields. It's the floor: the minimum return you'd ever accept for parting with your money.
WACC (weighted average cost of capital). The blended return a company must earn on its investments to satisfy both its lenders (debt) and its shareholders (equity) — equity investors demand a higher return than bondholders because they take on more risk, so WACC is always higher than the risk-free rate for a leveraged business.
Why this matters for a discount rate. Equity investors valuing a stock should discount at something closer to their required equity return (often approximated by WACC or a broad market-return baseline), not the risk-free rate — discounting risky cash flows at a risk-free rate systematically overvalues them by ignoring the extra risk you're taking on. Intrinsic's discount rate default (10%, floored at 7%) is anchored to typical long-run equity returns, not the risk-free rate, for exactly this reason.