Decodes Base64 information into human-readable text.

Base64Decode(1, 2, 3)

1stringRequiredLocation of Base64 text, either in variable or data extension field via Lookup() AMPscript function
2string.NET-supported character type used in decoding process, such as UTF-8 or UTF-16
3intIndicates whether the email send proceeds with incorrectly coded Base64 text. A value of 0 allows the send to proceed if send encounters an error. A value of 1 prevents the send from continuing if send encounters an error. Value defaults to 1.

If the value was 0, the send would continue and the email would contain an empty string instead of the decoded data.