High availability:

Database servers can work together to allow a second server to take over quickly if the primary server fails.

Load balancing:
To allow several computers to serve the same data.

Relpication:
master or primary servers:
Servers that can modify data are called read/write.

Slave servers:
Servers that track changes in the master are called standby or slave servers.
-> A standby server that cannot be connected to until it is promoted to a master server is called a warm standby server, and one that can accept connections and serves read-only queries is called a hot standby server.