technically there isnt much more I could tell you than the article Mike has already produced for you. The file systems handle things a tad differently. If your formatting for your phone you should go Fat 32 as its the most compatible file system to go with. Its also the easiest as it does not hold permissions in its instructions like ext2,3,4 or an ntfs. this is really nice when going from one device to another and when going from a device to a computer. If you never plan on using any kind of windows with the card and will strictly be using Linux then you can go with ext2 as that is the most common Linux system to use with usb thumb drives and micro SDCARDS as it has no journaling and doesn't need as much space as its cousins 3 and 4