BIP38 (BIP0038) or Bitcoin Improvement Proposal #38 is an implementation of passphrase-protected encrypted private keys for the Bitcoin protocol. For more detail you can read the proposal on GitHub here.
BIP38 encrypts and encodes a private key by making it passphrase-protected in the form of a 58 character printable string. The weakest part of encryption is typically the user's passphrase so it is very important to create a strong passphrase when it comes to encrypting your private keys.
BIP38 allows us to securely print a customer's private keys with the peace of mind that only the customer knows the passphrase to access the wallet. Please take the time to learn about BIP38 by reading the proposal on GitHub here.