Stored Procedures (what is it really used for?)

Question

So from a tutorial, I successfully created a stored procedure, stored it, and made code to use it. I think.
If I run my code, it seems to work fine, regardless of whether or not I have entered that stored procedure into the database.
Is my code suppose to work regardless? Is storing a procedure just meant to make my code, which repeats quite often, more efficient? Or are stored procedures created for different reasons? Are they there to let me run my java code from an sql query? I'm at my wits end trying to understand the significance of a stored procedure. I've posted my code, if it helps.
public static void callSortTwo(Connection conn, CallList cl) {
        try {
            Timestamp ts = new Timestamp(System.currentTimeMillis() );
            System.out.println("Executed at: " + ts);
            String insert_query = "INSERT INTO SWEATY_BALLSAK.CALLS (" +
                    "beat," +
                    "call_descr," +
                    "priority," +
                    "date," +
                    "time," +
                    "call_num," +
                    "location," +
                    "status," +
                    "entry_id) " +
                    "VALUES(?,?,?,?,?,?,?,?,?)";
            PreparedStatement pstmt = conn.prepareStatement(insert_query);
            for (int counter = 0; counter < cl.getSize(); counter++) {
                String current_event[] = cl.getElementArray(counter);
                pstmt.setString(1,current_event[0]);
                pstmt.setString(2,current_event[1]);
                pstmt.setString(3,current_event[2]);
                pstmt.setString(4,current_event[3]);
                pstmt.setString(5,current_event[4]);
                pstmt.setString(6,current_event[5]);
                pstmt.setString(7,current_event[6]);
                pstmt.setString(8,current_event[7]);
                pstmt.setTimestamp(9, ts);
                pstmt.executeUpdate();
        catch(SQLException sqle_callSort) {
            System.out.println("SQL Exception" + sqle_callSort.getMessage() );
        }

Answer 1

Stored procedures use PL/SQL, not SQL, find and read something about it, it is very wide topic.
Stored procedures are often used for efficiency reasons. Simple example: if stored procedure contains several embeded SQL statements, database has to parse and precompile these SQLs only once, during procedure's compilation. Second, database always optimizes each SQL query before execution - but in the stored procedure it is done only once, during compilation. When you execute SQL from your program, RDBMS must parse and optimize this SQL each time, so using stored procedure you could save some (little) time on parsing and optimizing.
But when you want to do some kind of 'batch procesing' - execute one query to take some data from the table, analyze this data, prepare next SQLs based on retrieved data and so on, it's always better to do it in the stored procedure instead of the program, because you avoid transferring data through the network from database to program and back - you call simply stored procedure and all the processing is done in the database.
Oracle from ver. 9, beside PL/SQL has something called "Java stored procedures', so .... yes, you could write stored procedures in Java too :)