Why does typing mysql -u root in the OpenServer console not establish a connection?

Question

PHP

Why does typing mysql -u root in the OpenServer console not establish a connection?
instead, a VERY long help message is displayed

spoiler

mysql Ver 14.14 Distrib 5.7.16, for Win64 (x86_64)
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Usage: mysql [OPTIONS] [database]
-?, --help Display this help and exit.
-I, --help Synonym for -?
--auto-rehash Enable automatic rehashing. One doesn't need to use
'rehash' to get table and field completion, but startup
and reconnecting may take a longer time. Disable with
--disable-auto-rehash.
(Defaults to on; use --skip-auto-rehash to disable.)
-A, --no-auto-rehash
No automatic rehashing. One has to use 'rehash' to get
table and field completion. This gives a quicker start of
mysql and disables rehashing on reconnect.

spoiler

Default options are read from the following files in the given order:
C:\Windows\my.ini C:\Windows\my.cnf C:\my.ini C:\my.cnf c:\openserver\modules\database\MySQL-5.7-x64\my.ini c:\openserver\modules\database\MySQL-5.7-x64\my.cnf
The following groups are read: mysql client
The following options may be given as the first argument:
--print-defaults Print the program argument list and exit.
--no-defaults Don't read default options from any option file,
except for login file.

Everything is not included, so I broke it into two short parts of the message that appears.

Answer 1

It is necessary to indicate not a hyphen "-", but a minus "-"