The Dunning-Kruger effect is as follows: "People with low skill levels draw wrong conclusions and make wrong decisions, but are unable to make mistakes because of their low skill levels".
Meaning: lack of understanding of mistakes made leads to a belief in one's own correctness and, consequently, to increased confidence in one's own decisions and in oneself, as well as to an awareness of one's own superiority.
Thus, the Dunning-Kruger effect is a psychological paradox that we all often face in life: less competent people see themselves as professionals, while more competent people tend to doubt themselves and their abilities. The lower the skill level, the higher the self-confidence.
At beginning of their research, Dunning and Kruger called Charles Darwin's famous statement:
"Ignorance breeds confidence more often than knowledge" and Bertrand Russell: "It is one of the unfortunate things of our time that those who are confident are stupid, and those who have imagination or understanding are full of doubt and indecision".