7 Days to Die community servers are multiplayer servers that are hosted and maintained by the community. This allows for a more customisable experience while playing including modified server settings, better support and even new features.
7d2d servers generally have 8-32 players. Any more than this can cause lag and other issues due to high resource consumption.
The recommended server requirements to host a 7d2d server are a minimum of 8GB RAM and 12GB HDD space.