The delete operation would delete the records and the free space would not be released for the other schema objects to use. (i.e. only the table whose records had been deleted would be able to use the freespace, for its futrure inserts) The operation of Truncate would preserce the schema, but would drop the recrds and release the freespace. This inturn would allow the other database objects to use this free space. It also would lower the high water mark accordingly.

Hope this would help you.
Sam