Syncthing is a free, open-source, peer-to-peer, continuous file synchronization program that works across multiple devices.
A Relay server can connect devices that can not directly be connected with each other (eg. firewall) or can be useful in case of low power devices as syncthing consums a lot CPU cycles to constancly identify changed filed and calculate deltas.
To help the community, reduce latency and increase its diversity, Libreops runs a syncthing relay in Greece.
If you want to help us run more relays, you can donate.