you want it to be safe? if you store your eth in exchange it's not safe, you need to store it in a hardware wallet, make sure you don't lose it, or use myetherwallet, keep the key, and never share it with anyone, never login to other peoples computer or in an internet cafe where you don't know if there is a keylogger or something, open your wallet to you own pc to make sure it's always safe.
To be safe, hardware wallet is not the only wallet to use. You can protect your cryptocurrencies if you are good at security for your passwords (wallet files, computer log-in sessions, etc.) and care about the websites you visit, then any link you receive (click on it or ignore it).
With MyEtherWallet, people can choose a password or not choose it.
Extra word
If you choose extra word, at least 9 characters, you will have a different wallet.
You can test it by create a wallet on Myetherwallet, choose extra words and try to log in your wallet with and without extra word.
You will get two different wallets with different addresses (after you log in).
If you send your ETH or ERC-20 token to extra word wallet, and don't save the extra word, you will lose those crypto. The wallet without extra word will be a different one and the ETH or ERC-20 token you send to extra-word wallet will not be existed in non extra word wallet.
Back up seed phrase and extra words.