Have favorite apps that buried under the pile of folders. I have many of them. Then, when I open them, their icons appear in my dock, that makes me feel happier.
However, when I quit those apps, they disappeared from my dock. Oh no, so much times needed to bring them to surface end in vain.. Feel depressed.. Maybe you can feel my feelings that time..
But now, I am happy, I know how to make my apps icon remain at my dock. And you will be happy too because I will share it to you.
Can you read those highlighted words?
Yes you are correct, your apps icon will stay calmly inside your dock, whatever you do to them, except you do this.