Many photography teachers shy away from the phrase, “Exposure Triangle,” and for good reason. The triangle itself has no meaning. First, there is no “light” leg. Second, it gives the viewer a mental picture of a non-existent relationship among the legs. But since there are three aspects of exposure that can be adjusted, it is natural to just call it a triangle. Moreover, it is a great term to enter into Google to find out about this concept (that is, everybody uses it).
Tony Northrup favors the use of sliders as a visual aid for these concepts. Here is a screen shot from one of his videos of this concept:
This imagery has advantages. In particular, if one of these sliders goes up, one of the other sliders has to go down in order to obtain the proper exposure.
Next: Primary effects of the Exposure Triangle