1) An extent is a set of contiguous blocks allocated in a database. In the Oracle database program, the first set of contiguous blocks, set up automatically when a segment is created, is called the initial extent. After the initial extent has been filled, the program allocates more extents automatically. These are known as next extents. The total number of extents that can be allocated in a database is limited by the amount of storage space available, or in some cases, by the program used.
2) The term extent is sometimes used in reference to any contiguous space (for example, a set of sectors) on a hard drive that is reserved for a particular file, folder, or application.