Please help me with Laman's terms

My program is complete and compiles very nicely.  I am on an extremely beginner level and understand some things but most of the things I do, I simply know that I am supposed to do them but do not exactly understand the why nor can I put things into laman's terms to understand them better.  Here is my program and I am asking for just brief explanations for better understanding of my program.  I will put ??? by things I hope someone can better explain.  Thanks a million !!

import java.io.*;
import java.lang.Math.*;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;  // Do I even need this or would java.lang.math be fine without this line ???

public class Mortgages

{
   

    public static void main(String[] args)

    {

            DecimalFormat twoDigits = new DecimalFormat("$###,###.00");

            
        double mortgage = 200000.00;
        double[][] yearsYearlyRate =  //Multiplies term by interest rate

       
        {
            { 7, 15, 30 },            
            { 5.35, 5.5, 5.75 }
        };

       
        double[][] monthsMonthlyRt =

        {
            {
                    yearsYearlyRate[0][0] * 12, yearsYearlyRate[0][1] * 12,
              yearsYearlyRate[0][2] * 12  // Provide brief description please
            },
            {
      // ????? I understand the above but need some clarification of the (1200)              
                    yearsYearlyRate[1][0] / 1200, yearsYearlyRate[1][1] / 1200,
                    yearsYearlyRate[1][2] / 1200
            }
        };


       
        for (int i = 0; i < 3; i++) // brief descriotion please of what this means

        {

            // ??? Please help here
            double payment = calPayment(monthsMonthlyRt[1][i], monthsMonthlyRt[0][i], mortgage);

           

            System.out.println("\nMortgage Amount \tTerm \t\tRate \t\tMonthly Payment");
            System.out.println("$200,000 \t\t" + yearsYearlyRate[0][i] + " years\t"
            + yearsYearlyRate[1][i] + "%\t\t" + twoDigits.format(payment));


            System.out.println("\nPayment # \tMonthly Interest Paid \t\tRemaining Loan Balance");

           
            interestBalanceList(mortgage, monthsMonthlyRt[1][i], monthsMonthlyRt[0][i], payment);

        }

    }

    // I totally do not understand what this entire double tmp or param thing means.  Please help !!!
    public static double calPayment(double param1, double param2, double mortgage) {


               double tmp = 1 + ( param1 ) ;
               for ( int i = 1 ; i < param2 ; i++)
               tmp = tmp * ( 1 + param1 ) ;
               double monthlyPayment = mortgage * tmp * param1 / ( tmp - 1 ) ;

      
       // double monthlyPayment = (param1 + param2 / (Math.pow((1 + param1), param2) - 1)) * mortgage;

              return monthlyPayment;
    }

   
    public static void interestBalanceList(double mortgage, double param1, double param2,
    double payment)

            {

       
              for (int i = 1; i < (param2 + 1); i++)  // Provide brief description please

        {


            System.out.println("Press 'ENTER' to view the loan amortization.");

            try

            {
                System.in.read();     // what exactly is this providing my program ???  Do I even need it ???
            }      catch (Exception e)


            {

            }

            // Calculate the Monthly Interest of the Loan Balance
            double monthlyInterest = mortgage * param1;

            // Calculate the Remaining Loan Balance
            double loanRemaining = mortgage - (payment - monthlyInterest);

            // Set the value of Mortgage Amount to the Value of the Remaining Loan Balance
            mortgage = loanRemaining;

            // Format the Monthly Interest Amount into U.S. Currency
            NumberFormat n = NumberFormat.getCurrencyInstance(Locale.US);
            String str = n.format(monthlyInterest);

            // Format the Remaining Loan Balance into U.S. Currency
            NumberFormat num = NumberFormat.getCurrencyInstance(Locale.US);
            String string = num.format(loanRemaining);

            // Display the Payment #, Monthly Interest Paid and Remaining Loan Balance


            System.out.println("\n " + i + "\t\t\t" + str + "\t\t\t" + string);  // Please explain the string

        }
    }  // Also, I would like to make the program pause after showing 12 payments on the screen so
       // how would I go about doing this ?????
}