Their role is to implement each set of rules or guidelines so that users don't violate their boundaries in terms of the types of content they post and share.
Consequently, this leads to a more positive environment in which users are free to interact without the risk of encountering unacceptable social behavior online.
Increasing the safety of each member of the community ultimately increases trust in the business.
But you can't really talk about it in a nutshell, so I would suggest reading an article on the subject https://newmediaservices.com.au/content-moderation-3-reasons-why-it-is-crucial-for-your-business/
and dealing with it thoroughly if you really care about it.