Is Image Noise Removal Image Enhancement or Image Restoration Operation? I am working in digital image processing field, recently I am studying about Image Noise, I just want to know that whether this noise removal is part of image enhancement or image restoration. 

I have read some papers on it, at some points authors are saying that image enhancement from a given noisy image, and on the other hand in some papers authors are saying that noise removal is image restoration process.

Please explain what is correct?.
It depends on the final goal and the model used.
If we assume we have an image - $ I $ which is a result of a sum on of an image $ W $ with noise $ n $: $I = W + n$ and our goal by reducing the noise is estimating $ W $ than this process is restoration.
Yet I could try achieving a different goal by denoising, such as making it look better (Subjective target) or use prior such as Piecewise Constant image which means the denoising process if more of an enhancement to the image.