Digital images can come in different file formats. For example JPG, GIF, TIFF, PNG, BMP, PICT and more. The reason there are so many different types of image files is because there are many different ways to compress images.

Compress means to make the files size smaller. Different file formats are used to compress images for different purposes.

JPG is generally the best file format to use for compressing photographs. It can compress an image to a small size while still leaving you with a very good image quality. JPG compression also allows you to choose the level of compression so it can be quite flexible for different purposes. Digital cameras generally save photos in a JPG format automatically. JPG is a format used for nearly all web images so it is safest to use these.

GIFF files are mostly used for vector graphics or files that have large blocks of colour and little or not tonal contrast. It is not that good to use for photographic images. 

PSD Photoshop's files have the PSD extension. It is the best file format to use while you are editing a photograph in Photoshop as it keeps all the necessary digital information for that program. However, be sure to save your end result as a standard JPG, or you may not be able to use it for other purposes later on.

TIFF Most graphics programs that use TIFF do not use compression. This means that the file sizes are quite big. TIFF is not widely supported by web browsers, and should be avoided for web use.

The best file formats for the internet (for emailing, uploading to a website, etc) is JPEG for photographs (such as the image above) and GIFF for graphics with limited colours.

When saving images for the internet you must make sure the pixel dimensions are less than 800 x 600 pixels and that the file size is ideally less than 1MB.

You can use free software to reduce your images file size such as Resize. Download this software under the Links section here.