The practice began with the dead. Its older Chinese name concerns the siting of graves, and the earliest sustained literature is about where to bury an ancestor so that the descendants prosper. Siting the houses of the living came later and remained secondary for a long time, which is why so much of the classical vocabulary is funerary.
Two broad approaches developed and both are still taught. The form school reads the landscape directly, assessing the shape of hills, the course of water and the way a site is enclosed or exposed. The compass school works from a graduated instrument, the luopan, with concentric rings carrying the trigrams, the stems and branches, the constellations and the directions, and calculates from the orientation of a building and its date of construction. The two are combined in practice, and lineages differ in how much weight each carries.
What reached the English-speaking world in the late twentieth century is a simplified derivative and should be identified as such. In the best known Western form an eight-sector grid is laid over a floor plan and aligned with the front door rather than with the compass, and each sector is assigned a life area such as wealth or relationships. That alignment is not how the compass schools work, and the life-area scheme is largely a modern addition.
Both are real practices with real practitioners. They are not the same practice, and a reader is entitled to know which one is being described.