What is the different between encode and encription?

private string base64Encode(string sData)
          {
              try
              {
                  byte[] encData_byte = new byte[sData.Length];
                  encData_byte = System.Text.Encoding.UTF8.GetBytes(sData);
                  string encodedData = Convert.ToBase64String(encData_byte);
                  return encodedData;
              }
              catch (Exception ex)
              {
                  throw new Exception("Error in base64Encode" + ex.Message);
              }
          }

public string base64Decode(string sData)
           {
               System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
               System.Text.Decoder utf8Decode = encoder.GetDecoder();
               byte[] todecode_byte = Convert.FromBase64String(sData);
               int charCount = utf8Decode.GetCharCount(todecode_byte, 0, todecode_byte.Length);
               char[] decoded_char = new char[charCount];
               utf8Decode.GetChars(todecode_byte, 0, todecode_byte.Length, decoded_char, 0);
               string result = new String(decoded_char);
               return result;
           }