Have you ever seen book covers that are made of portraits shots filled with words? This effect is called Typographic portrait, and consists on replacing the values of the pixels with text characters, preserving the outline of the overall image; therefore, you will look at it distantly and recognize the shape, even distinguish the image, but if you are close enough you will realize the image is made out by text.
Adobe Photoshop as the versatile tool for designers that it is can give us a wide range of effects to fit our needs; so in this case it is going to be our tool used for this tutorial. If you want to learn how to create a typographic portrait in Photoshop follow up this guide.