An appreciation will motivate the personAll human beings want to get the attention of others. If somebody is appreciating the good work done by a person in the presence of some other people, he will get the attention of other people at least for a moment. That attention will act as inspiration and he will try further to improve his performance so that he will get the attention and recognition. That will motivate him.
But nobody likes to get criticised openly. They may feel ashamed and their efficiency may further come down as they get demotivated with the remarks made openly. So when you want to point out the mistakes of somebody do that privately. That will be helpful to the individual to develop himself.