That's the Jedi Knight Enhanced mod that make everything sharper?
He's referring to the High Detail Mod. It forces the game to use its highest quality textures and models at all times, rather than use lower quality versions at medium and long distances. Naturally, this also eliminates "popping" that would ordinarily occur when the game switched between qualities. This mod doesn't add any textures or models to the game, so it improves the game's graphics while still being "vanilla."
Jedi Knight Enhanced replaces some of the game's models (and their textures) with higher quality ones taken from Jedi Knight II. In other words, things like Stormtroopers and the blaster rifle, which both games have, will look as good in JK as they do in JK2.
Jedi Knight Retexture Pack replaces many of the game's textures, mostly textures for surfaces (ex. walls), which aren't covered by JK Enhanced.
If you want the absolute highest quality graphics, apply all three mods. Each one improves things that the other two don't touch. For example, JK Enhanced and JK Retexture Pack do not replace every model and texture, respectively, so the ones that they don't replace will still benefit from the High Detail Mod. Note, though, that JK Enhanced and JK Retexture Pack require the Unofficial Patch (get it from PCGamingWiki.com) to be installed, since they use higher resolutions of textures than the original game executable supports.