Ideally, for true split lighting, you’ll want to have the face directly bisected through the middle, without a gradual shift from light to dark.
This pattern is exactly what it sounds like; it splits the face into two parts, one illuminated and one in shadow. To get the look, place your key light at a 90-degree angle on the right or left side of the subject’s face, at around eye-level. Ideally, for true split lighting, you’ll want to have the face directly bisected through the middle, without a gradual shift from light to dark. Needless to say, this look is a dramatic one; feel free to use that fill card on the shadow side to soften the contrast.