What is the difference between Muslim , Mumin and Muhsin ?
If you are an arabic reader you can check a detailed explanation for the Hadith That was a conversation between the Prophet PBUH and a foreign Arab who came to ask about Islam, Iman, and Ihsan.
The difference between these three is the following:
So as a summary the difference is that Islam is to be done with your actions, however Iman is more related to your heart and beliefs.
In the verse 49:14 we can see the difference between Islam and Iman.
Ihsan is the most highest level among them. This verse 16:128 shows how the Mohsin has a high grade from his God, because of the fidelity between a person and his God.