It is defined as a two part antenna consisting of a vertical
portion and a reflective or ground portion. When constructed properly, it is
very similar to a vertically oriented dipole.
The reflective portion is not always a physical element, but
often a natural earth ground (where the soil conductivity is sufficient) or
ground “radials” (a set of wires just beneath the ground that act as the
reflective portion).
For example, a λ/4 vertical antenna when grounded, the earth
acts as a mirror and the system acts as an antenna of double size i.e. λ/2
dipole. It is as shown in fig. the radiation pattern of it will be similar to vertical
λ/2 Hertz antenna.
