...
FHE = Fully Homomorphic Encryption.
You can read a nice intro here:
https://blog.cryptographyengineering.com/2012/01/02/very-casual-introduction-to-fully/
And more details here: https://en.wikipedia.org/wiki/Homomorphic_encryption
Basically:
“Homomorphic Encryption” means you can perform certain operations on the encrypted objects, and you get the same outputs (still encrypted, of course) as if you had performed the operation on the unecrypted objects.
“Fully Homomorphic Encryption” allows arbitrary operations on the encrypted objects to get the same outputs. And of particular relevance for our application, supports both addition & multiplication.
...