A journaling file system is a special type of file system that maintains a tracking file, called a journal. The journal enables the system to repair any inconsistencies that may arise as a result of a system halted abnormally. It does this by keeping track of changes that are made before committing them to the main file system. In the event that the computer is not shut down properly, any data loss can be recreated. This type of file system is therefore less likely to suffer from corruption, and brings file systems back online quickly.

via Choosing a Journaling File System – Linux Links – The Linux Portal Site.