There are many types of vulnerability scanning tools out there. Some are commercial products, so you need to pay for them. These products typically have refined GUIs and are easy to use with great reporting functionality. These include scanners such as Rapid7, Qualys, and Tenable. There are others out there that are free. These include products such as OpenVAS, Retina CS, and Nexpose. These free tools are often not as easy to use and don't always have as many features as the paid versions. However, in my experience, OpenVAS is a great free tool. Nessus was one of the most popular free vulnerability scanners until they closed-sourced it, and since then requires an annual subscription.

Vulnerability scanners are designed to scan through an environment and look for known vulnerabilities within the network parameters. Depending on the product, there could be 10,000+ known vulnerability within vulnerability scanner product that can be used against targets. These types...