WAL-E is a tool designed specifically for interacting with various cloud services and PostgreSQL. Cloud services are often designed to require complex API calls before accepting read or write commands. This makes it somewhat difficult to send them arbitrary files such as PostgreSQL transaction logs we wish to save in a secure location.
The principal benefit of keeping WAL files in a remote cloud location is the same as maintaining offline backups. By moving transaction logs to an external server, we can use them in emergencies or complete datacenter disasters. It's a different form of high availability where we trade the expense and latency of involving distant servers for a major increase in geographical diversity.
WAL-E supports transmitting and retrieving files to several cloud vendors and APIs: