Tag Image File (or Tag Image File Format) is one of several file types for storing photographic images.
TIF files are loss-less, meaning that image quality is preserved during editing and multiple resaves.
TIF images can be saved with no data compression, or with a compression called LZW to reduce file data size on your computer.
Other common photo formats include JPG, PSD, and GIF. Less common formats include RAW, BMP, and PCT.