What is the difference between inbound and outbound web service? In inbound I must consuming a wsdl? or should I expose my service?
Is there a difference between the type of communication? Synchronous or asynchronous?
Inbound webservice is something which your website will consume. There could be webservices published by some other 3rd party tool. You can import that webservice and use that to call methods from 3rd party tool.
Oubound Webservice is something that you publish from your server and 3rd party tools consume it to get data/record from your server.
I hope that made some sense.