The image above is a low resolution image. This means when i enlarge it, it will become pixelated, as shown in the image. The image resolutions are shown as DPI, meaning dots per inch. DPI can go from 1DPI – 600+ DPI. 
The image above this is a high resolution image, meaning when i enlarge it the quality of the picture will stay at a good quality.
Lucia Felici's Blog 