Que sont les classes de collection en C# ?

using System;
using System.Collections;

namespace CollectionsApplication {
   class Program {
      static void Main(string[] args) {
         //creating two bit arrays of size 8
         BitArray ba1 = new BitArray(8);
         BitArray ba2 = new BitArray(8);

         byte[] a = { 60 };
         byte[] b = { 13 };

         //storing the values 60, and 13 into the bit arrays
         ba1 = new BitArray(a);
         ba2 = new BitArray(b);

         //content of ba1
         Console.WriteLine("Bit array ba1: 60");

         for (int i = 0; i < ba1.Count; i++) {
            Console.Write("{0, -6} ", ba1[i]);
         }
   
         Console.WriteLine();

         //content of ba2
         Console.WriteLine("Bit array ba2: 13");

         for (int i = 0; i < ba2.Count; i++) {
            Console.Write("{0, -6} ", ba2[i]);
         }

         Console.WriteLine();
         BitArray ba3 = new BitArray(8);
         ba3 = ba1.And(ba2);

         //content of ba3
         Console.WriteLine("Bit array ba3 after AND operation: 12");

         for (int i = 0; i < ba3.Count; i++) {
            Console.Write("{0, -6} ", ba3[i]);
         }

         Console.WriteLine();
         ba3 = ba1.Or(ba2);

         //content of ba3
         Console.WriteLine("Bit array ba3 after OR operation: 61");

         for (int i = 0; i < ba3.Count; i++) {
            Console.Write("{0, -6} ", ba3[i]);
         }

         Console.WriteLine();
   
         Console.ReadKey();
      }
   }
}

Bit array ba1: 60
False False True True True True False False
Bit array ba2: 13
True False True True False False False False
Bit array ba3 after AND operation: 12
False False True True False False False False
Bit array ba3 after OR operation: 61
True False True True False False False False