Exploitation is the active use of a software weakness, misconfiguration, or logic flaw to make a system do something it was not meant to do. An attacker may exploit a bug to run code, bypass authentication, steal data, or gain a foothold inside a network.
In cyber security, the term matters because a weakness is only a theoretical risk until it is exploited. Once exploitation begins, defenders must assume the vulnerable service may already be probed from the internet or used in an attack chain. This is especially dangerous for exposed systems such as edge appliances, web applications, and remote access services.
In real incidents, exploitation often follows public disclosure of a flaw or is combined with other weaknesses to build a working attack path. Defenses focus on rapid patching, reducing exposure, monitoring for suspicious requests, and confirming whether vulnerable systems are still reachable.