A Group 5 element is the series of elements in group 5 (IUPAC style) in the periodic table, which consists of vanadium (V), niobium (Nb), tantalum (Ta), and dubnium (Db).
All of these elements are classed in Group 5 because their valence shell holds five electrons. Dubnium can only be produced in the laboratory, it does not exist in nature.