What is the means of exception in .Net code example

Example 1: exception in asp.net c#

try
{
    //code that may raise an exception
}
catch
{ 
    // this catch block must be last block
}
catch (NullReferenceException nullEx)
{
    Console.WriteLine(nullEx.Message);
}
catch (InvalidCastException inEx)
{
    Console.WriteLine(inEx.Message);
}

Example 2: exception in asp.net c#

class Program
{
    static void Main(string[] args)
    {
        Console.Write("Please enter a number to divide 100: ");
        
        try
        {
            int num = int.Parse(Console.ReadLine());

            int result = 100 / num;

            Console.WriteLine("100 / {0} = {1}", num, result);
        }
        catch(DivideByZeroException ex)
        {
            Console.Write("Cannot divide by zero. Please try again.");
        }
        catch(InvalidOperationException ex)
        {
            Console.Write("Invalid operation. Please try again.");
        }
        catch(FormatException  ex)
        {
            Console.Write("Not a valid format. Please try again.");
        }
        catch(Exception  ex)
        {
            Console.Write("Error occurred! Please try again.");
        }
    }

}