PostgreSQL recovery file syntax, ver 8.4 vs ver 9.5

In postgreSQL version 8.4 it seems that you can place the db server into warm standby mode with the following setting in recovery.conf

    restore_command = 'pg_standby archiveDir %f %p %r'

In postgreSQL version 9.5 I see the same option, but I also see what appears to be an alternative syntax in recovery.conf:

   standby_mode = (boolean)

   trigger_file = (string)

So is this new syntax an alternative to the old syntax (both are accepted by PGSQL)? Any benefit to the new syntax?

Does the new syntax mean that I can use the restore_command setting as well (to use my own copy command)?