TOS stands for Terms of Service. They are binding rules that define what you can and can’t do on the site.
For example, Facebook has a TOS. Many groups and events have supplemental rules set by the organiser. This is also allowed.
If the TOS is broken, they can remove you from the network, and as with the spaces of others, respecting their rules is only right, and will ensure you can remain to interact.
You should always read the TOS and rules.