Lab-created or synthetic diamonds are "real" but they are not "natural".  Synthetic diamonds cost a fraction of what a mined diamond costs, but they are (usually) chemically the same as "natural" diamonds. Telling the difference between a natural and a synthetic diamond requires a trained professional using highly sophisticated equipment which tends to rely on detecting the higher uniformity (closer to perfect) structure that gem-quality lab-created diamonds usually have as well as distinctive trace quantities and uniform distribution of specific non-carbon elements within the diamond crystal.  Man-made diamonds do not command the same re-sale value as mined diamonds due to successful PR campaigns by the mined diamond industry to suggest that mined diamonds are better than lab-made diamonds because they were mined instead of "made". If you care about re-sale and insurance values it is important to know if the gem is "natural" or "man-made". Diamond and moissanite are very easy to mistake for each other. It is difficult to tell the difference between them but moissanite sparkles a little more than diamond and also produces a double refraction, which can be difficult for most people to see. You can try shining a light through a stone, and if it gives off a much more colorful and large shine than a known diamond, then you'll know that moissanite is what you have. Diamond and moissanite have very similar thermal conductivities.  If you only use a diamond tester, it will show "diamond" when you actually have moissanite. It is important to test any stone that tests "diamond" on a diamond tester or a moissanite tester. For a professional jeweler, the best option is to just get a combined diamond/moissanite tester. White topaz is another stone that can look a little like a diamond to the untrained eye. However, white topaz is much softer than diamond. A mineral's hardness is determined by its ability to scratch and be scratched by other materials. A stone that can scratch others easily without being scratched itself...

TL;DR in Chinese:
识别合成钻石。 识别莫桑石。 识别白色托帕石。 识别白色蓝宝石。 识别立方氧化锆。