PNG is a raster graphic data storage format that uses lossless compression algorithm to Deflate. PNG was created as a free format to replace GIF. PNG supports three main types of raster images: grayscale image, a color indexed image and the color image. PNG format stores graphical information in a compressed form.
ICO is a file of this format usually contains a small image icons of different resolutions (16x16, 32x32, 64x64 pixels) and various color depths (16 colors, 32, 64, 128, 256, 16-bit, and so on). Used to display files and folders in the graphical user interface (GUI) operating systems. This format can be opened with the help of the program ACDSee.