If you have not yet read it, I'd advise you read the JDBC API Documentation (supplied with Sun's JDK), and the JDBC Specification. Both are available from http://java.sun.com/products/jdbc/index.html.
http://jdbc.postgresql.org contains updated information not included in this document, and also includes precompiled drivers.
If you see anything in the documentation that is not correct, does not match your experience with the particular feature or requires further clarification, please use this form to report a documentation issue.