Withdrawing staked tokens and rewards involves exchanging your stETH or rETH for ETH and stMATIC or MaticX for MATIC, directly with the relevant protocol. For more information on withdrawals, see here.
A swap involves trading your liquid staking tokens back for ETH, MATIC, or other available tokens, often via a third-party exchange, and does not typically involve shutting down a validator. Swaps are subject to fluctuating market prices. To easily swap your liquid staking tokens through the MetaMask Staking interface, find the position you’d like to exit from, click the three dots on the right next to your position, and click 'Swap'.