Four days a week is where a lot of lifters settle, and it's a smart place to be: enough sessions to split the body sensibly (usually upper/lower twice, or a push/pull arrangement), but not so many that life, sleep or recovery start losing. It's the split that survives a busy week — miss one and you've still trained three times.
What actually drives results on a 4-day split isn't the exact template, it's progressing the weights and giving each muscle 48-ish hours to recover before you hit it again (which a good 4-day layout does for you). This builder structures the four days around your goal, experience and equipment, and tracks your lifts so you can see the progression. Just try it with your schedule and see the plan it builds.