What is the difference between resizing and resampling?

The main difference between resizing and resampling  an image is very simple.  Resizing is actually as simple as it sounds, you change the size of the image without changing the number of pixels in the image.  Image resampling, however does involve changing the number of pixels in the image.  This is done in photoshop simply by checking a box in the Image size dialog box.  You can ge to it by going to the image menu at the top and then choosing image size. You have several options once the dialog box is open.  The first is Pixel dimensions (width and height), document size (width, height, and resolution), and the checkboxes at the bottom, scale styles, constrain propotions, and resample images.  For Pixel dimension this is something you would work with when saving images for web page use.  Document size is controling how to actually print your images.   The resample image box is checked by default, so to just resize you simply uncheck it.  You will notice when you do this it will grey out some of the options in the Pixel dimensions section.  You can only adjust document size options.  The scale style and constrain proportions boxes are also greyed out when you uncheck the resample image box.

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