Yes both scampi and langoustine are the same thing but just with different names.
The main difference and really only difference between the scampi and langoustine is in the name.
Some people call them scampi and other people call them langoustine.
The names for either can be different in different places but they are the same thing.
However scampi and prawns are different because scampi and langoustine belong to the lobster family and prawns to the shrimp family.
So while scampi and langoustine are the same the prawns are what are different.