[osaariki]

Exactly. And the magic is that now you can securely compute aggregations of data you've stored without having to download all of your data.

Say you have some field in all of your encrypted, cloud-stored records and want to find the sum of all of them. With traditional encryption you'd either have to trust the cloud with your decryption key or download all of the records for local processing, which could be very slow. With homomorphic encryption you can instead have a cloud service do that computation without any visibility to the actual values and only have to download a single ciphertext containing the result.