Unless you explicitly share a voice with another account or to the Voice Library, the voices you've created in My Voices (previously VoiceLab) are only accessible through your account.
Professional Voice Clones and voices generated using Voice Design can be shared. You can share individual voices with specific friends and colleagues via a sharing link (Voice Designed voices) or whitelisting (Professional Voice Clones), but you can also share Professional Voice Clones with the community via the Voice Library.
If you share your Professional Voice Clone with the Voice Library, you have the option to receive financial rewards when someone uses your voice, or alternatively you can earn back spent credits. Voice sharing options and metrics for Professional Voice Clones are only available if you're on the Creator plan or above.
It's not possible to share voices created by Instant Voice Cloning.
To find out more about sharing, you can read this article: How do I share a voice?