You can save several assets in your Earn wallet to earn interest. Assets saved in Flexi Earn can be withdrawn at any time, meanwhile assets saved in Locked Earn will be received in active balance (along with the interests) after the lock period ends.
Whereas for Staking, you can only save PTU. Staking interest will be received in your active PTU balance every day. Other than earning interest, you can also get various benefits. Withdrawing your PTU Staking balance will take 7 days until the asset received in your PTU active balance.