The "native currency" of the Brave browser — you can read more here: https://basicattentiontoken.org/. As the URL implies, the name is "Basic Attention Token" for some reason. Didn't really work out, but has a huge marketcap even though no one uses it: https://coinmarketcap.com/currencies/basic-attention-token/.

Market cap is just a function of multiplying total shares by the last share sell price, no?

pretty much, just replace "shares" with "supply".

Interesting