Session state is a workspace that contains all variables with their values for one user.
Session state can be maintained:
See the “Maintain session state attribute” of the “Source” section of an item.
Session state are variable.
You can use the APEX_UTIL package to get and set session state,
With:
BEGIN
APEX_UTIL.SET_SESSION_STATE('my_item','myvalue');
END;
BEGIN
:MY_ITEM := :MY_SECOND_ITEM;
:MY_ITEM := 'myValue';
END;
BEGIN
SELECT 1 INTO :MY_ITEM FROM DUAL;
END;