Final answer:
Synthetic rubies are crafted from aluminium oxide with chromium as a dopant to create the characteristic red color, while ruby simulants are different substances that only mimic the look of natural rubies.
Step-by-step explanation:
Synthetic rubies are made from aluminium oxide (Al2O3) with trace amounts of chromium to give them their red color, while ruby simulants are materials that resemble rubies in appearance but have a different chemical composition. Synthetic rubies are created through processes like the flame fusion method, also known as the Verneuil process, or the hydrothermal process which mimic natural ruby formation conditions. On the other hand, ruby simulants can be made from a variety of materials, including glass, plastic, or other crystalline materials such as garnet or spinel that are dyed to match the appearance of rubies.