People can see objects because they block the passage of light waves. If you want to make a ball invisible, you can cover it with a layer of metamaterial arranged in the shape of a concentric circle, which can block all light waves and does not reflect or absorb. The blocked waves meet again on the other side of the object and continue to travel in a straight line. To the observer, the object seems to become non-existent and visual invisibility is realized. in short, the metamaterial used in the invisibility cloak allows radar waves, light, or other waves to pass around the object without being bounced. in order to achieve an invisible effect. In the future, the invisibility cloak will be first used in the military field to improve the concealment and security of operations. But if anyone can achieve invisibility, it will also cause a series of social problems.
The meaning of this passage is that objects block light waves so that people can see.