tl;dr a 'parse tree' for how their (transformer based) LLM weights the import of the tokens in a given prompt. The authors noticed patterns in the visualization that they felt imitated relationships that we would regard as related.
That's as much as I can summarize, given my ignorance.
user-aRxb[attentionviz.pdf]> summarize the document's contents
bot> Querying GPT...
bot> This paper describes AttentionViz, a tool designed to provide a global view of Transformer Attention that can be used to identify sentence view, clusters of search results, semantic behavior, and fine-grained attention patterns; experts have suggested additional interaction modes and global search patterns to be used to quickly scan for and compare attention trends.
That's as much as I can summarize, given my ignorance.