Technically, there are three sets of tonsils: the pharyngeal
tonsils, commonly known as adenoids, the palatine tonsils, and
the lingual tonsils. People refer to tonsils usually as the
palatine tonsils, which are oval, pea-sized clusters of lymph
cells at the opening of either side of the throat. Their role is
to filter bacteria and viruses and produce white blood cells and
antibodies. Tonsils are the first line of defense as part of the
immune system.
Adenoids or pharyngeal tonsils are clusters of lymphatic tissue
in the back of the nose, above the roof of the mouth. They begin
to shrink by age 7 or 8, are barely visible by the late teens,
and completely gone by adulthood. Adenoids are covered with
cilia and mucus. The small hairs wave about to spread mucus,
which is carried to the stomach by swallowing. The purpose of
the mucus is to capture infectious bacteria, dust, and other
particles and flush them away.
Bottom line, all adenoids are tonsils, but not all tonsils
are adenoids.