Update extensions.rst

source/accounts/extensions.rst

@@ -2,7 +2,7 @@
 Extensions
 ************
 
-| The **Extensions** define the information needed for an endpoint such as a hard phone, soft phone or some other device. The extension is the SIP username and password and together they are a key part of the credentials needed to authenticate to the server.
+| The **Extensions** define the information needed for an endpoint such as a hard phone, soft phone or some other device to connect to the SIP server. The extension is the SIP username, the password is the secret used for authentication and the domain name servers to purposes it locates the server to register to and is the realm that determines which domain the endpoint is registering to.
 
 *  Extension 	
     Enter the alphanumeric extension. The default configuration allows 2 - 7 digit extensions.