  Interaction-free measurements introduced by Elitzur and Vaidman [Found. Phys.
23, 987 (1993)] allow finding infinitely fragile objects without destroying
them. Many experiments have been successfully performed showing that indeed,
the original scheme and its modifications lead to reduction of the disturbance
of the observed systems. However, there is a controversy about the validity of
the term ``interaction-free'' for these experiments. Broad variety of such
experiments are reviewed and the meaning of the interaction-free measurements
is clarified.
