Hello!
Gotland is an island of Sweden, and in the medieval times, they issued some of their own coins (which were also said to be popular in the older times of Livonia).
Right now, there are only three coins from Gotland listed on Numista. I was planning to add more, but all three of those coins are listed under Denmark. That does make some sense, seeing as how those coins were issued when Gotland was under Danish rule, but this place also minted coins when they were under Sweden (and when they were under the Kalmar Union). So rather placing Gotland's coins in different sections of the catalogue, creating a new issuer for this place would keep them all together.
Thank you for reading!
(And here are a few coins from Gotland: https://www.numisbids.com/n.php?p=sale&sid=1881&cid=49533.)