A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
For questions specifically about the Geometry Shader stage in the GPU pipeline.
Questions about image-based height-field representations, commonly used to represent a terrain.
Compositing is the combining of visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene.