A compliment is a praise or apology that is made to someone or something, highlighting their characteristics, behaviors, merits, physical or intellectual qualities, etc. The compliments have positive effects on the psyche of the person who receives it, since it generates a really positive influence on the personality and character.
Most psychology specialists consider that giving and receiving praise can be healthy as it helps improve self-esteem.
For example, a person starts work in a company and after the first week receives congratulations and praise from their supervisors, this will motivate them to continue doing an excellent job. The same happens with children, if parents (every time their children get good grades or excel in any other activity), take on the task of praising their work and effort, these children will feel much more confident and motivated to continue exercising their activities efficiently.
There are people who use praise to try to make a profit, these people are known as flatterers and usually their praise is not entirely real, they simply say it to take advantage of it. For example, an employee begins to praise her boss's wardrobe for how beautiful she is that morning (although in reality the lady is dressed horrible), only to get permission to leave earlier.
It is important to mention that both the excess of praise and the lack of it can be counterproductive for the individual. When someone receives praise and more praise all the time, they can end up becoming conceited and believe themselves superior to others; While if you do not receive any praise, you will feel that what you do has no merit and your self-esteem will end up falling. Therefore a healthy balance must be maintained between the two.