Everything not in the portfolio or the header for one reason or another.
badbunsen in the wild | propaganda (promo material)
Anything that promotes this site.
These were—and in some circles still are—effective ways to
spread your website at the time. If you were around for the glory days of
Geocities, or have seen a neocities website or two, there's a good chance
you saw an 88x31 button for, say, Netscape, or someone's webring.
Me, being a late zoomer, only experienced this through Neocities and the Internet
Archive, but they're still fun to spread as it can give you an insight into a
webmaster's interests or favorite sites.
TL;DR, if you really like this site and would like to link to it on your personal website, use these buttons.