I think the workings of Tailscale have been answered pretty well already.
As far as ideas for server usage go, I have a similar setup with the following excerpt of most used apps on my server:
- PiHole for DNS filtering and custom internal DNS entries for my devices/services
- Unbound DNS server to free myself from public DNS resolvers (Google, Cloudflare, Quad9 and the likes)
- Unifi Controller (for my Wifi APs)
- ResilioSync (for syncing important files between all my devices and server)
- Homeassistant + Mosquitto (MQTT Broker) + ESPHome for all home automation
- Huginn (scrapes the web for changed content or news and creates notifications for me on Telegram or Discord, maybe somewhat comparable to IFTTT but self-hosted)
- Homebox (home inventory management)
- ActualServer (budgeting app)
- Jellyfin (media streaming)
- an assorted collection of apps I refer to as the "High Seas", which are Radarr, Sonarr, Lidarr, SABnzbd, etc.
Bitteschön :-)
Ein Klassiker, gut gealtert und thematisch aktueller denn je :D