Implementing a PostgreSQL 9.6 streaming replication on Linux Ubuntu 18.04 servers is very easy.
In the streaming replication mode, the standby connects to the primary, which streams WAL records (Write Ahead Log) to the standby as they're generated, without waiting for the WAL file to be filled. Streaming replication allows a standby server to stay more up-to-date than is possible with file-based log shipping.
The standby server can be in read only mode for reporting purposes for example.
A replication slot ensures that the needed WAL files for the standby are not removed in the primary server before the standby server processes them. Multiple replication slots can be defined depending on the number of the standby servers.