Image noise usually manifests itself as random speckles on a smooth surface which affects quality of the image.
Learned about Image Noise when building Rubiks
3 types of image noises
Random Noise
Fluctuation of the colors above the actual intensity of the image
Fixed Pattern Noise
Appears after long exposures and high temperatures
Banding Noise
Camera is reading data from the sensor and it directly relates to the in-camera technology factors
To remove image noise you can try
Gaussian Blur
Gaussian Blur tends to remove high frequency noise while at the same time it’ll soften edges heavily.
Median filter
Median Filter in Photoshop preserves edges and works best when dealing with noise with high spatial frequency.
Actions and Presets
Many presets available for Photoshop and Lightroom