Disclaimer: It is always safer to use a tool like Universal Android Debloater (UAD) which reads from a community-tested database, rather than manually running pm uninstall -k --user 0. If you manually uninstall, keep the -k flag to keep the data in case you need to factory reset to get the app back.
These packages serve no essential purpose, track your data, serve ads, or are leftover carrier/OEM testing apps. Removing these will free up RAM, battery, and storage.
com.facebook.appmanager(Facebook background bloat)com.facebook.services(Facebook background bloat)com.facebook.system(Facebook background bloat)