A covered call means selling a Call option while already owning the underlying shares. If the price rises above the strike and the Call is exercised, you deliver shares you already own, rather than needing to buy them at a potentially much higher market price — meaningfully reducing (though not fully eliminating) the risk compared to selling a naked Call.
The Trade-Off
In exchange for the premium collected, upside on the shares is capped at the strike price (plus premium received) — a neutral-to-mildly-bullish income strategy, not a protective one.
Related Reading
See the full strategy with a worked example in Covered Call Strategy Explained With Example.