What is Mel spectrogram as an audio sequence and how do I apply it?

I was under the impression that Mel-spectrograms were simply spectrograms with mel scale as the y axis. However, recently, I read in a research paper this line "Data representations such as Mel-Spectrograms can be seen from two different perspectives: either as an image, or as an audio sequence." What does this mean? It implies Mel-spectrograms are not just spectrograms, but can be interpreted in another way. If so, what is it exactly, and how can it be applied?