“The fool doth think he is wise, but the wise man knows himself to be fool.”
– William Shakespeare , As you like it.
Imposter syndrome is psychological phenomenon in which people instead of attributing success to their genuine effort, attribute it to luck, timings, or having deceived others into thinking they are more competent than they believe themselves to be.
They refuse to believe that they are competent and they have succeeded due to their intelligence and competence and not just luck.
Opposite of this is Dunning- Kruger effect; here an incompetent person will tend to overestimate his own level of skill.
Just imagine talent review between employee suffering from imposter syndrome and his boss from Dunning- Kruger effect :-)