Backblaze is a cloud storage company with two main products. Computer Backup is a backup service: a small program on a Mac or Windows computer copies the files to Backblaze's data centers, so that they can be restored when the originals are lost. B2 Cloud Storage is object storage, a service that keeps files as objects reached over the internet; it is S3 compatible, which means programs written for Amazon S3 can use it.
Computer Backup runs automatically and continuously. It backs up all user-generated data on the computer and on connected external drives, with no limit on file type or size. A 2048-bit public/private key pair protects the AES-128 key that encrypts the data, and a user can add a private key. Restores come through the web as zip files of up to 500 GB, or on an encrypted USB drive that is mailed free if it is returned within 30 days. Business accounts add central management of many users.
Both are hosted services. Computer Backup is a flat subscription per computer with unlimited data; B2 is billed per terabyte stored each month.