Just to clear things , this is what my understanding is of index fragmentation :

1)internal frag - physical , happens at the leaf level , ie. index grows .

2) external frag - logical , pages grow and scanning takes longer.

Now , our sys.dm_db_index_physical_stats view gives us the external frag only , right ? in percentage ?

What about the internal frag ? How do we find it ? And does it lower down when an index is defragmented ?