Translation:Good evening, Samia! Good evening to you, Mohamed!
Good news! They have explain this matter in the TIPS skill :)) We can visit it via this link: https://www.duolingo.com/skill/ar/Introductions_greetings/tips-and-notes
it's not meant to be logical or literal. the word نور is often used to mean brightness, happiness, good things, etc. for example, my mom often calls my brother "نور عيني" (literally, the brightness of my eye). there is no نور or brightness in my mom's eye; she just uses that word as a term of endearment.