RAW – A Raw image is named raw because it contains no image compression so you get maximum information that is recorded on the image sensor from the camera.
Raw image files are sometimes called digital negatives because the fulfil the same role as negatives in film photography, raw images cannot be directly used as an image because it saves as a file but has all the information that is needed to create an image.
JPEG – JPEG images are also known as a lossy compression files, this means that with raw files you can open and save them as many times as you want within an editing software however JPEG files compress themselves everytime you open and save them losing information and eventually the image becomes pixelated and loses quality.
TIFF – TIFF stands for ‘Tagged image file format’ they are used for storing very large high quality images. It is prefered to used either tiff or raw files for manipulation programs such as Photoshop & Lightroom. If your printing TIFF is the best files to print from because there is no compression and printers generally read TIFF files the best.
PSD – A PSD is a Photoshop Document, it allows you to come back to your editing that you have done keeping all the files and layers, A PSD is a lossless file because it does not lose any information when you save and keeps it there for you to come back to at anytime.