CMDB means Configuration Management database
CMDB is a tool for registering information about applications. The goal of a CMDB is to keep track of all accurate information about the applications that are managed by an organization. You have to think about passwords, locations, version, necessary hardware, etc. It is information that is especially important for IT services. A CMDB offers an organized overview of the available data, with a possibility to filter in different ways to get the right information (quickly).