Oracle Database Discussions

Hi,
in documentation I see :

SQL> show sga
 
Total System Global Area 1048576000 bytes
Fixed Size                   782424 bytes
Variable Size             259002280 bytes
Database Buffers          788529152 bytes
Redo Buffers                 262144 bytes


SQL> show parameter pool
 
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
buffer_pool_keep                     string
buffer_pool_recycle                  string
global_context_pool_size             string
java_pool_size                       big integer 0
large_pool_size                      big integer 0
olap_page_pool_size                  big integer 0
shared_pool_reserved_size            big integer 12373196
shared_pool_size                     big integer 0
streams_pool_size                    big integer 0

My question is : what is in Variable size ?
Is ther any relation between sqlarea and variable size ?
Thank you.