Cygnus A (i.e., 3C 405 or QSO B1957+405) is a radio galaxy,
one of the first identified.
As a radio source, it was discovered by Grote Reber in 1938, with his
back-yard radio telescope, the first radio receiver built
for that purpose.
An apparent quasar was discovered within it in the 1990s: this
is now no mystery since quasars are interpreted as active galactic nuclei (AGNs),
which are also often the driver for strong radio emission
from galaxies.
Cygnus A demonstrates the involvement of jets in creating a
radio galaxy's radio emission; its strongest radio signal comes
from two regions in opposite directions from the galaxy itself.