excellence / doing beautiful deeds
Masculine verbal noun (maṣdar) of أَحْسَنَ (Form IV). Related: حُسْنٌ (beauty/goodness), حَسَنَةٌ (good deed), مُحْسِنٌ (one who does iḥsān), أَحْسَنُ (best/most beautiful).
Iḥsān is the highest level of faith, defined by the Prophet ﷺ as 'worshipping God as though you see Him, and if you cannot see Him, then knowing He sees you.'