The higher the resolution the more dots per inch, allowing more detail and color enhancement.
Image resolution determines the maximum resolution for printing.
The monitor resolution determines the size of the displayed image. If the image resolution is 150 dpi and the monitor resolution is only 72 dpi, then the image will be displayed as more than twice as large on the monitor as it really is. Values for pixel depth usually range from 1 to 24 bits per pixel. The number of pixels in an image is fixed and therefore increasing the size of the image will decrease its resolution and decreasing the size of an image will increase its resolution. To see the image size and resolution in Photoshop , hold down the Option key and click on the lower left corner below your image.