Understanding Asma’ al Husna (The names of Allah): What is the difference between the two names of Allah (سبحانه و تعالى) ar-Rahman (The Merciful) and ar-Raheem (The Compassionate)?
Source: The Risale-i Nur Collection by Ustadh Bediuzzaman Said Nursi from the Sunni school.
Summary: The name ar-Rahman (The Merciful) is The One Who is merciful in the general sense. The name ar-Raheem (The Compassionate) is more specific and not necessarily inclusive of all creatures.
This is a video related to my blog post: Difference Between The Merciful (Ar-Rahman) and The Compassionate (Ar-Raheem)