He is saying that you can have multiple wallet files in Electrum...

The "default" wallet name is called "default_wallet"... when you attempt to create new wallets it will call it will first suggest the name "default_wallet", if that already exists it will try "wallet_1", then "wallet_2" etc. However, if you choose a custom name like "MySuperSecretWallet" then that is what the file will be called. As Electrum does NOT use a file extension (like .dat) the wallet files are called named whatever you use for a wallet name.

Note that this has pretty much no relevance to your issue whatsoever and I have no idea why the guy posted it.