The built-in function, ng:base64 converts a string (text) into a base64 based string. This can e.g. be used, if you want to insert any kind of data into an XML node, without substituting any characters, that are not allowed.
This function is related to the functions: ng:base64ToUTF8, ng:base64EncodeFile and ng:base64EncodeResource.
This can e.g. be used, if you want to insert dynamic images directly in the contents of an email.
Here is an example:
This XPath expression:
ng:base64('INTERFORM')
outputs this string:
SU5URVJGT1JN