You got your terminology all mixed up. Unposted GL transactions (journal entries) remain in the GL10000 (Transaction Header) and GL10001 (transaction detail) until, well, they are posted. Once a GL journal is posted, header and detail records are left joined to produce a single entry per distribution account into the GL20000 table. The GL20000 table contains journals for all open year(s). When the year-end procedure is performed and the year is closed in GP, the records in GL20000 move to the GL30000 table (history) for the year that was closed.
The Description column is common to GL10001, GL20000, and GL30000. So when you post a journal or close a fiscal year, the value follows through.
