What does sweep mean in Electrum and how is it different from restoring a key?
You entered a private key in Electrum and you're not sure if that's enough or if you need to make a transaction.
Sweeping a key **sends your funds with a real transaction to a new wallet**; restoring only **shows where they are**.
What each one does
According to the Docs de Electrum (sweep), sweeping a key sends your funds with a real transaction to a new wallet; restoring only shows where they are.
Restoring is like looking at your balance: the wallet reads the key and lets you see and use the funds, but nothing moves. Sweeping is a transaction that removes the funds from that key and puts them in the wallet you choose.
What happens with the fee and the chain
Sweeping pays a network fee and the transaction stays on-chain. Restoring costs nothing because there is no transaction.
So if you just want to see your balance, restoring is enough. If you need to move funds away from a key that may be compromised, sweeping puts everything into a new wallet.
Why restoring doesn't protect you if the key was exposed
The data doesn't say restoring is the same as securing. If someone saw the key, restoring doesn't change that the person could sweep the funds before you.
Sweeping creates a real transaction that competes for the same balance; whoever gets confirmed first keeps the bitcoin. That's why with an exposed key, the advice is to sweep as soon as possible to a new wallet.
Why restoring doesn't protect you if the key was exposed
The fact only says what each action does, not that restoring is enough. If someone else saw the key, restoring it in another wallet doesn't remove the risk: the funds stay at the address controlled by that key. To move them out, you need to sweep.
Source: Docs de Electrum (sweep)