You probably know someone who thinks a little too much of themselves, especially about their capabilities. All awhile you probably think you really can't do your job, that you've somehow managed to fool everyone about your expertise.
The latter you've probably heard of: it's called the impostor syndrome. You may have a piece paper (aka degree certificate) that says you can do this. But inside your head you find your work going at least a little bit over your head, more often than not so far over you fail to grasp it. But the former? Believing in the illusion of one's high capabilities or overall superiority is one cognitive bias called the Dunning-Kruger effect.
And oh boy, is the world twisted: people suffering from the impostor syndrome are usually of higher intelligence. People demonstrating the Dunning-Kruger effect are usually of lower. As Bertrand Russel said:
One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision.
To top the sundae with a cherry, members of neither group recognize that they're in that particular group. Impostors truly believe they are incompetent. Dunning-Krugers truly believe they know their stuff.
I should imagine the Dunning-Kruger effect being the reason behind people being rather unemployed than working minumum wage jobs. Because they think they're above those jobs. They think the society owes them an executive position. And a high pray grade. When the truth is that all they're owed is a kick in the butt for thinking too much of themselves. (A hint of self-irony intended.)
So how can you figure out if you're in one of these groups? Easy. Do you think you're qualified for your job?
If yes: Ask your boss if they think you're doing enough work and if the work you do is of adequate quality.
If no: Ask your boss if they think you're doing enough work and if the work you do is of adequate quality.
If you and your boss agree - that your answer for the first question is the same as your boss's answer for the second question - you're in neither group and have a good sense on the state of the matter.
If you and your boss disagree - that you think you're qualified (or more than qualified) and your boss thinks you're not, or vice versa - you either suffer from the impostor syndrome (you say no, they say yes) or demonstrate the Dunning-Kruger effect (you say yes, they say no).
The point here is that you need an external opinion on the matter, and you must get it from an objective stand (so not your mother). Supervisors are usually required to tell you the truth when questioned like this. It's kind of in their job descriptions. And if you suspect your boss fears you and may not tell you what they really think of you, ask other people who have seen you work. (If they fear you as well, congratulations - there's no limit how high you can get promoted in your firm.)
So whether you think you're an impostor or don't know you're a Dunning-Kruger person or know you're neither, make sure or figure it out. You'll be better off when accepting reality.