The discussion clarifies that a histogram is appropriate for representing the frequency of letters in a message, as it charts the distribution of a single variable. Participants note that while both terms can apply, a histogram specifically represents numerical data, raising questions about whether letters qualify as such. Concerns are expressed about ensuring clarity and accuracy in terminology for a lesson plan submission. Additionally, suggestions are made to enhance the overall quality of the graphs, emphasizing the importance of labels, titles, and design elements. Ultimately, the consensus leans towards using "histogram" while acknowledging the flexibility in terminology.