1. what is the difference between read and synchronous read in file adapter?
Read is use for polling. Read option will initiate a new instance(and you will use a receive activity - inbound).
2. how synchronous read operation is outbound operation? Read must be an Inbound operation.
Synchronous read is being used from an existing instance (process). You will use an invoke activity for that - you are sending a request to read a file (file/directory name etc..). You are then getting back the result (file content etc....).