Update README.md

Author: boolpath

README.md

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 #The WebWallet API
-A digital wallet specification for the Web.
+###A digital wallet specification for the Web.
 
 ## Abstract
 This specification defines an API that aims to enable Web applications to carry out electronic commerce transactions using WebWallets.
 
 ## What is a WebWallet?
 A WebWallet is a digital wallet that can temporarily store money on the Web for intended online purchases.
+
++ **No deposits, but recharges**  
+A WebWallet is funded through prepaid recharges, and funds can be added in any currency supported by the target merchant and the applicable regulations.
+
++ **No withdrawals, only payments**  
+A WebWallet recharge is interpreted as a purchase intention, therefore it cannot be reversed. The balance loaded on a WebWallet cannot be redeemed for cash, so it must be spent on a purchase at some point.
+
+
+## API Overview
+The WebWallet API defines how to expose and interact with WebWallet instances in order to request and carry out transactions.
+
++ **Exposure through URLs**  
+Each WebWallet is represented as a URL, and transactions can be requested and carried out using HTTP methods with the proper credentials.