We write our documents, read our emails, use our websites and so on. As these systems have evolved to make our lives easier, so has the ability to compromise them become ever greater.
In many cases systems are compromised silently, often being used to distribute spam emails, or as part of denial of service attacks, and we can be blissfully unaware. Often the only way to find out if our systems have been compromised is to actively look for offending malware, or for telltale signs of its presence.
A basic security health check will identify the component parts of your network and systems and identify whether they are sufficiently secure, or if further work is required to reduce risk to your network.
More comprehensive checks or audits can be made to discover if malware may already be present, or more work is required to ensure risk is minimised.