FAT32 is a filesystem format that is used on flash drives and older systems. It is the only filesystem that is fully supported by all three major operating systems (Windows, Mac OS X, and Linux).
FAT32 (File Allocation Table or File Allocation Table) is a file system that organizes and manages access to files on hard drives and other media. Created in 1996 by Microsoft to replace the FAT16 used by MS-DOS and with a number of limitations. FAT32 was implemented on Windows 95 (OSR2), Windows 98 and Millennium, and still has compatibility with Windows 2000 and Windows XP, using a more modern file system, NTFS, which was continued, and is also used in systems Windows Vista, Windows 7 and Windows Server 2008 R1/R2 (enterprise server).
The file allocation table (FAT) is a data structure that Windows creates after formatting a physical unit. This table stores information about the location of each file within the physical drive so they can be saved, retrieved, modified or deleted later. They are stored in blocks arranged in different positions of the disk, justifying the need for a table that point to each of these blocks. In summary, for any type of data access to media, you need a file system to take these actions. Without a structure for storing data such as FAT32, no procedure for disk access is possible.