Engine Flushing is the process by which , the deposits due to action or chemical process changes of engine oil(Usually mineral oil), are formed.
This can be either by not changing oil at correct interval or with long term of the vehicle.
As your car has clocked 1 lakh km,you can go with engine flushing as it will enhance the engine life.
In some ASS
, they do engine flushing (Which is a Scam)
If you are doing engine flushing at 1 lakh km,next engine flushing is required only after another 60k km.