Updated README.md

README.md

@@ -1,6 +1,59 @@
 # IbanEx
 
-Library for working with IBAN numbers (parsing, validating and checking and formatting)
+Elixir library for working with IBAN numbers (parsing, validating, checking and formatting)
+
+## What is an IBAN?
+
+IBAN (which stands for International Bank Account Number) is an internationally agreed code made up of up to 34 letters and numbers which helps banks make sure that international transfers are processed correctly.
+
+In just a few letters and numbers, the IBAN captures all of the country, bank, and account details you need to send or receive money internationally. This system is used throughout Europe, and also recognised in some areas of the Middle East, North Africa and the Caribbean. Find IBAN examples for every country where it's used.
+
+## HowTo Use
+
+### Successfull case to parse IBAN
+
+Parse string with valid formatted IBAN from supported country
+
+```elixir 
+{:ok, iban} = "FI2112345600000785" |> IbanEx.Parser.parse()
+IO.inspect(iban)
+IbanEx.Iban.pretty(iban)
+```
+
+#### Response
+
+    %IbanEx.Iban{
+      country_code: "FI",
+      check_digits: "21",
+      bank_code: "123456",
+      branch_code: nil,
+      national_check: "5",
+      account_number: "0000078"
+    }
+    
+    "FI 21 123456 0000078 5"
+
+### Errors cases of IBAN parsing
+
+Parse strings with invalid formatted IBANs from unsupported and supported countries
+
+```elixir
+{:error, unsupported_country_code} = "AZ21NABZ00000000137010001944" |> IbanEx.Parser.parse()
+IO.inspect(IbanEx.Error.message(unsupported_country_code), label: unsupported_country_code)
+
+{:error, invalid_length_code} = "AT6119043002345732012" |> IbanEx.Parser.parse()
+IO.inspect(IbanEx.Error.message(invalid_length_code), label: invalid_length_code)
+
+{:error, invalid_checksum} = "AT621904300234573201" |> IbanEx.Parser.parse()
+IO.inspect(IbanEx.Error.message(invalid_checksum), label: invalid_checksum)
+```
+
+#### Response
+
+    unsupported_country_code: "Unsupported country code"
+    invalid_length: "IBAN violates the required length"
+    invalid_checksum: "IBAN's checksum is invalid"
+
 
 ## Installation