It is a graphical device for describing how some elements of communication relate. What those elements are (and how many) varies depending on who is building the pyramid, which may be either upright or inverted.
For example, last month Fred E. Miller blogged about one with three levels. He didn’t mention that these oft-repeated. and rather mythical, percentages are from Albert Mehrabian. Calling them a pyramid is putting an old whine in a new bottle. On his web site Mehrabian cautioned that they are not universal, and to:
“...Please note that this and other equations regarding relative importance of verbal and nonverbal messages were derived from experiments dealing with communications of feelings and attitudes (i.e., like-dislike). Unless a communicator is talking about their feelings or attitudes, these equations are not applicable....”
In her book Point, Click & Wow! Claudyne Wilder described another type of Communication Pyramid:
“The inverted pyramid depicts four levels of communication, from the most basic form of conveying data to the highest level of suggesting its meaning for the future by sharing a vision.”
There was a seven-level upright pyramid described in a magazine article titled "Don’t Misconstrue Communication Cues: Understanding MISCUES can help reduce widespread and expensive miscommunication." You can read the text here or here.
In March MIchael J. Maher blogged about a different seven-level pyramid. Also, Kessels & Smits have described another three-level pyramid.
So, there are lots of pyramids other than the great one at Giza.