named commands 是什么意思?

我在 mysql --help 里看到这个选项:-G, --named-commands
                      Enable named commands. Named commands mean this program's
                      internal commands; see mysql> help . When enabled, the
                      named commands can be used from any line of the query,
                      otherwise only from the first line, before an enter.
                      Disable with --disable-named-commands. This option is
                      disabled by default.这个 named command 是什么?谢谢!