Gemini is a light-weight text-first protocol and markup format sometimes referred to as "Gemtext".

=> Gemini Quickstart | Gemini in Circumlunar Space | Gemtext introduction | Gemtext cheatsheet

If you’re looking for a wiki about Gemini related software, check out the Gemini space. There, you’ll also find a list of Gemini clients.

=> Gemini Space

If you're asking for a recommendation: are you an Emacs person? Use Elpher. Are you a Python person? Use AV-98. Anything else, I don’t know. There’s the problem of compiling the other clients yourself. Some of them offer binaries from their release pages.