This is a special web portal for viewing a suite of products that focus on fronts and cyclones, as derived from ECMWF model output. "CDB" is shorthand; it stands for "Cyclone DataBase". One geographical domain is available, spanning Europe and the North Atlantic. The products are based on automated identification techniques described in several papers (e.g. from 1998, 2010).
Products include automated synoptic charts, on which low-level fronts and cyclonic features are marked, 'front spaghetti' charts, strike probability charts for cyclones in different wind-strength categories, 'clickable' charts for viewing the tracks and characteristics of particular cyclones, and 'dalmatian charts' where spots denoting cyclones in different model runs are overlaid. Different products focus on windstorms, snowstorms and rainstorms.
For further information on how to interpret the products go here (link is also accessible within the portal).
For examining forecasts for tropical cyclones ECMWF provides a separate set of products listed in the Tropical Cyclones page.