Meaning of python -m flag

From Python Docs:

Since the argument is a module name, you must not give a file extension (.py). The module-name should be a valid Python module name, but the implementation may not always enforce this (e.g. it may allow you to use a name that includes a hyphen).

Package names are also permitted. When a package name is supplied instead of a normal module, the interpreter will execute <pkg>.__main__ as the main module. This behaviour is deliberately similar to the handling of directories and zipfiles that are passed to the interpreter as the script argument.

If you type python --help

You get

// More flags above
-m mod : run library module as a script (terminates option list)
// and more flags below

A great many things in a terminal will show you how to use it if you either use command --help or man command

The -m stands for module-name.

From Command line and environment:

python [-bBdEhiIOqsSuvVWx?] [-c command | -m module-name | script | - ] [args]

When -m is used with a python statement on the command line, followed by a <module_name>, then it enables the module to be executed as an executable file.

You can refer to python docs for the same, or run python --help