Help to understand with the encryption algorithm code

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
				 
		String^ STR =tbString->Text->Trim();
		array<byte>^ buffer = Encrypt( STR, key );
		Encoding^ ascii = Encoding::ASCII;
		String^ decodedString = ascii->GetString( buffer );
		tb_Encrypted->Text = decodedString;

		String^ plaintext = Decrypt( buffer, key );
		tb_Decrypted->Text = plaintext;


			}

array<byte>^ Encrypt( String^ PlainText, SymmetricAlgorithm^ key )
{

   // Create a memory stream.
   MemoryStream^ ms = gcnew MemoryStream;

   // Create a CryptoStream using the memory stream and the 
   // CSP DES key.  
   CryptoStream^ encStream = gcnew CryptoStream( ms,key->CreateEncryptor(),CryptoStreamMode::Write );

   // Create a StreamWriter to write a string
   // to the stream.
   StreamWriter^ sw = gcnew StreamWriter( encStream );

   // Write the plaintext to the stream.
   sw->WriteLine( PlainText );

   // Close the StreamWriter and CryptoStream.
   sw->Close();
   encStream->Close();

   // Get an array of bytes that represents
   // the memory stream.
   array<byte>^buffer = ms->ToArray();
   //String^buffer = ms->ToString();
   // Close the memory stream.
   ms->Close();

   // Return the encrypted byte array.
   return buffer;
}


// Decrypt the byte array.
String^ Decrypt( array<byte>^CypherText, SymmetricAlgorithm^ key )
{

   // Create a memory stream to the passed buffer.
   MemoryStream^ ms = gcnew MemoryStream( CypherText );

   // Create a CryptoStream using the memory stream and the 
   // CSP DES key. 
   CryptoStream^ encStream = gcnew CryptoStream( ms,key->CreateDecryptor(),CryptoStreamMode::Read );

   // Create a StreamReader for reading the stream.
   StreamReader^ sr = gcnew StreamReader( encStream );

   // Read the stream as a string.
   String^ val = sr->ReadLine();

   // Close the streams.
   sr->Close();
   encStream->Close();
   ms->Close();
   return val;
}

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