Need help to understand SQL query (oracle10g) [closed]

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I'm new in SQL and need little help to understand parts in this SQL statement

select BUY_VALUE,
    SELL_VALUE,
    RATE_DAY,
    RATE_TIME
from ( SELECT TRIM (b.ticker),
           TRIM (TO_CHAR (b.buy_value, '9999999.99')) BUY_VALUE,
           TRIM (TO_CHAR (b.sell_value, '9999999.99')) SELL_VALUE,
           b.currency, 
           TO_CHAR (TRUNC (SYSDATE), 'YYYYMMDD') rate_day,
           TO_CHAR (SYSDATE, 'HH24MISS') rate_time 
         FROM portal.gpb_bank_quotes b
         WHERE b.ticker = 'GAZP'
     )

1. what is b (b.buy_value) ?
2. FROM portal.gpb_bank_quotes - is that table name? Is it possible that it delimited with .
3. ahhh too difficult ///

Thanks in advance

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1. b is a table alias for portal.gpb_bank_quotes. This is handy so that you don't have to type portal.gpb_bank_quotes.buy_value, etc.

2. Yes. portal is a schema, and gpb_bank_quotes is a table in that schema.

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b is an alias for the table/view gpb_bank_quotes which is located in the schema portal.

EDIT - as per comment from OP:

The SELECT ... FROM ( SELECT... FROM...) is just using the inner SELECT as a subquery.

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The same result for this query could also be obtained without the outer select. The TRUNC on SYSDATE is also redundant if specifying the date format to TO_CHAR

SELECT TRIM (TO_CHAR (b.buy_value, '9999999.99')) BUY_VALUE,
       TRIM (TO_CHAR (b.sell_value, '9999999.99')) SELL_VALUE,
       TO_CHAR (SYSDATE, 'YYYYMMDD') RATE_DAY,
       TO_CHAR (SYSDATE, 'HH24MISS') RATE_TIME 
  FROM portal.gpb_bank_quotes b
  WHERE b.ticker = 'GAZP';