AEM In MSM

There is a huge amount of documentation on this topic. The MSM provides a functionality to re-use the content across different languages and maintains the relationship to the source in the form of rollout configs. So whenever there is a change to the source, all the targets would get updated.

See below links for more detailed info:

https://docs.adobe.com/content/help/en/experience-manager-learn/sites/translation/multi-site-manager-feature-video-use.html 

https://docs.adobe.com/content/help/en/experience-manager-64/administering/introduction/msm.html

http://www.aemcq5tutorials.com/tutorials/configure-multi-site-manager-msm-in-aem/

Thanks,

Singaiah