Port 25565 is the default public listener for Minecraft Java servers. People searching this question usually want a fast answer to one problem: can other players actually reach the server from the public internet?
Interpreting results
open: the handshake completed from the probe vantage.closed: the host responded, but nothing accepted the connection on that port.timeout: the handshake never completed, which often means a firewall, NAT problem, or a stale DNS target.
Best next step
Run the Kordu Probe check first, then compare that with a local listener check on the server itself. That tells you whether the issue is on the service host or between the host and the internet.