NST work by utilising two things: style and content. Here content refers to object, structures etc in the image and style refers to texture and colors.
Below are the categories of NST. It has not been discussed in detail as I will be covering them later.
During each iteration, the target image gradually transforms, capturing the style patterns while retaining the content structure.
The swirling effect is clearly visible in the final image. Hence we can say that the style has been transferred to the content image.