A virtual phone number is usually a particular mobile number that which is not connected to any phone physically or to a SIM-Card by the phone company.
When you have a virtual Mobile Number, you will be able to answer incoming calls with an application across the networks.
2 way SMS starts when the message is sent by the client to short or long code. This message received by the short or long code is then delivered through to the ‘PULL’ server by the mobile operator.
The server, in turn, processes the message based on the keyword. The incoming messages are delivered back to the client’s web application by initiating a reverse ‘PUSH’ process.