The Third Extended File System (ext3 or ext3fs) is a file system for the Linux kernel. It is basically ext2 with a journal. A journal is a special file used to repair any inconsistencies that occur as the result of an improper shutdown of a computer.
ext3 was a very popular file systems and a default file system for many Linux distribution, but ext4 has taken its place in a last couple of years.
ext3 supports files up of up to 2 TB, file systems of up to 16 TB, and filenames of up to 255 characters. It is backward compatibile with ext2.