maybe there are some plastic products or products with plastic parts at hand, when looking carefully, you can find some of them have textures or lettering on their inner or external surface.

you do know those textures and lettering are molded during molding process, they are just for an aesthetic aid or for incorporating identifying information, either for end users or term of molding, Texturing sometimes can hide surface defects such as knit lines and other surface imperfections. But they have their own manufacturing standard, for example, the depth is limited, and extra draft needs to be provided.