The part where the human is shown. I have the original image in color and want to convert it into the red effect. What is the effect called and what technique is used.
The image you have attached was not created using an effect - this is actually a well-executed vector illustration. You may achieve similar look in Photoshop but the outcome will be nowhere near the provided illustration in terms of quality.
Image > Adjustments > Thresholdand drag the threshold slider until you achieve a satisfactory result.
For a more detail result, you would have to redraw the image. You can do it in Photoshop, but it'd be much easier in Illustrator.
Steps in Photoshop:
Pen Tool, draw the darker parts of the image.
The process will kind of look like this, excuse my poor execution, but hopefully the idea is clear!: