[NTG-context] OpenType and XeConTeXt

Hi, using ConTeXt with XeTeX seems to be an nice option for us MacOSX users. But I get always confused with the names for these rich features like Style Option, Ligatures, Variants. I mean: how do I know how many variants and style options a font has and how they and their ligatures etc. want to be called? In plain ConTeXt (for the 255 characters) we can use \showfont[...] and \showcharacters in order to know how to call the specific characters/glyphs. But what about OpenType? Peeking at the LaTeX side of XeTeX, I saw that they have created a packages called fontspec which seems to give better access to all (?) if these options. What about us? Is there help also for XeConTeXt? Thank you, Steffen