The Oracle TRUE condition is returned when an expression is evaluated that satisfies the expression's test. The simplest form of this is "does Value_1 equal Value_2"?
1 = 1 will return TRUE because the expression is evaluated as being true (that is, '1' really does equal '1').
1= 3 WILL return FALSE.
'cat' = 'dog' will return FALSE.
However, TRUE may be returned as the test for a non-empty set. For example, you have a table named 'Users' which contains a row where the column 'First_Name' has the text 'john' in it.
SELECT * FROM Users WHERE First_Name = 'john'
The result of the SQL above will return a positive number of rows. The result of the SQL expression is considered 'TRUE' and any logical test on the result would be evaluated as 'TRUE'.