RFC is a communication interface that provides the ability to call a function remotely from another SAP System or Non SAP System.

Each function module has a defined interface through which data, tables and return codes can be exchanged. The only difference between calling a function module remotely and locally is a extra parameter which is provided remotely that specifies the target server on which the function module should be executed.

There are 3 types of RFCs:

1. Synchronous RFC call: The calling program stops until the function module executes on the target server and returns results.
2. Asynchronous RFC call: The calling program runs in parallel with the function module on the target server. The target system must be available.
3. Transactional RFC call(tRFC): Several function modules are grouped into a transaction. They are processed in the target system in the sequence in which they are called.