Your node key earns and holds your rewards. If you lose it (uninstall, clear browser data, or a new computer) the node cannot be recovered. Save an encrypted backup and keep it somewhere safe. You will need this password to restore it, so do not lose the password either.
This replaces the wallet in this browser. Import an encrypted backup file and its password to move or recover a node. Back up the current one first if you want to keep it.
The raw, unencrypted key. Anyone who has it fully controls your node and rewards. Only reveal it somewhere private, and prefer the encrypted backup above.
Backups use the standard Web3 keystore format (scrypt + AES), the same as MetaMask and geth, so they are portable. Keys never leave your device except in a backup file you choose to save.