COMMAND 命令与直接在shell输入的命令有什么区别?

COMMAND 命令与直接在shell输入的命令有什么区别?

COMMAND 命令与直接在shell输入的命令有什么区别?      
man command查command, 里头有详细的

电脑出了点问题, 死活不能粘贴, 呵

      
command [-pVv] command [arg ...]
              Run  command  with args suppressing the normal shell function lookup. Only builtin commands or commands found in the PATH are executed.  If the -p option is given, the search for command is per-
              formed using a default value for PATH that is guaranteed to find all of the standard utilities.  If either the -V or -v option is supplied, a description of command is printed.   The  -v  option
              causes  a single word indicating the command or file name used to invoke command to be displayed; the -V option produces a more verbose description.  If the -V or -v option is supplied, the exit
              status is 0 if command was found, and 1 if not.  If neither option is supplied and an error occurred or command cannot be found, the exit status is 127.  Otherwise, the exit status of  the  com-
              mand builtin is the exit status of command.
理解不透,请详细解释并举例.
谢谢!      
引用:
Only builtin commands or commands found in the PATH are executed
关键是这句话
复制内容到剪贴板
代码:
$ alias ls='echo "no ls any more"'       ## alias 别名
$ ls                                                            ## 执行这个别名
no ls any more
$ command ls                                        ## 这才是我们想要的
abc               books            dwhelper           mbox         mysql-ldd    study        svn_repository
      
明白了,十分感谢!