A memo and a comment — what is the difference, and when are they required?

Internal Comment

— Internal comments are optional.
— The internal comment feature allows you to add notes to your transactions for personal reference.
— These comments are not sent to the blockchain and do not affect transaction fees.
— NC Wallet optimises your transactions by not storing extra data on the blockchain. Your internal comments are only visible to you in your transaction history, helping you keep track of your activities without any additional costs.

Memo/Tag

— A memo/tag is a comment that goes to the blockchain with a crypto address and amount.
— It is optional for blockchain but may be required by some recipients, such as some crypto exchanges. They use this field to identify your account and deposit funds.
— If a memo/tag is mandatory, the recipient will provide it along with a crypto address. In this case, you must fill it out in the Memo/tag field on the Send screen. Remember that all transactions in the blockchain are final, make sure to enter it correctly.
— In NC Wallet, currently, a memo may be required by a recipient only for assets on the TON blockchain.