There are certainly overlaps between the different modules, but we have made sure that they build on each other. The "network module" offers a lot for communication with each other. The "Private Messaging System" is ideal for private conversations. To network their contacts, use the Community Builder. On the top level you will find the user administration tool of "Joomla".
On all levels you will find profiles that we ask you to maintain. The most far-reaching is probably that of "Community Builder".
We have summarized all menu items under "Network". We suggest that you simply try everything out and find out what works best for you.