A connection timeout occurs when a device attempts to communicate with a server or another device but does not receive a response within an expected time window. Rather than waiting indefinitely, the system cuts off the attempt and returns an error. 

Timeouts are a normal part of how networks handle unresponsive connections. Without them, your browser or application could stall indefinitely waiting for a reply that never comes. The timeout threshold is typically set by the application, operating system, or server, and can range from a few seconds to much longer, depending on the context. 

Several factors can trigger a connection timeout. The destination server may be down or overloaded, the request may be blocked by a firewall, or there may be significant packet loss along the route between your device and the server. Network congestion, misconfigured servers, and long physical distances can all contribute as well.

When troubleshooting a timeout, tools like ping and traceroute can help identify where the break is occurring along the network path.