what is rowid ,

i kown this is  definiens  of rowid

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   The ROWID in Oracle8/8i is externalised as an 18 digit character string
   with the format 'OOOOOOFFFBBBBBBSSS' where:

       OOOOOO = is a base 64 encoding of the 32-bit dataobj# (Data object
                number was introduced in 8.0 to track versions of the same
                segment because certain operations can change the version.
                It is used to discover stale ROWIDs and stale undo records)
          FFF = is a base 64 encoding of the relative file number
       BBBBBB = is a base 64 encoding of the block number
          SSS = is a base 64 encoding of the slot (row) number

what is rowid used for ?

can i use this select sql: