I thank Maurizio Pagani for allowing me to publish and translate his interesting presentation, published on http://babel.it.
OpenVAS is a framework that includes services and tools for scanning and the complete managment of vulnerability.
A vulnerability scanner is a tool that allows you to scan a target system (IP/HOSTNAME) based on a range of ports and a set of policies. The tool is supported by a database that is used from the vulnerability scanner to analyze possible problems whenever you find a listening service. The tool that scans receives daily updates from the database Network Vulnerability Tests “NVTs”.