What is the purpose of ExportCredentialSuffix?

[timmc-edx]

When using assume, I get the following warning:

[!] No credential suffix found. This can cause issues with using exported credentials if conflicting profiles exist. Run granted settings export-suffix set to set one.

For that command, the closest I can find in the docs is just this:

Export Credential Suffix: The ExportCredentialSuffix option enables appending a suffix when exporting credentials.

Questions this leaves me with, which should probably be answered in the docs:

1. What is a credential suffix?
2. What happens if I don't have one?
3. What happens if I do have one?
4. How do I choose a suffix?