What is resizing images and size guide in Adobe Photoshop?

When working with images for a website and any design , you will need to resize your images to suit your   particular purpose

  basic guide that can help you decide on what is suitable. (The units used here are

pixels, which are standard units across all computer platforms. The conversion between pixels and

inches is roughly1inc =72 pixels or1cm =28 pixels) To use this particular unit of measure you will

need to adjust you preference settings by selecting Edit > Preferences > Units and Rulers and

changing the units and rulers to measure in pixels

if you want to resize a picture look on the menu bar and select Image > image size