What is mu-plugins, do I need to install that?

Dear Support, do I need to install mu-plugins for the domain mapping to work? I already installed the domain mapping plugin, but haven’t configure it yet.

I have read the following 2 posts at your site.

https://premium.wpmudev.org/manuals/wpmu-manual-2/using-mu-plugins/

https://premium.wpmudev.org/manuals/installing-mu-plugins/

I couldn’t find the “mu-plugins” plugin.

Thank you,

Imad Daou