Horizontal Well
A well that drills down to a target zone, then turns and runs sideways through it for thousands of feet to expose far more reservoir rock.
A horizontal well drills vertically to the target formation, then curves and runs sideways — laterally — through the productive zone. Instead of crossing a thin reservoir at one point, it stays inside it for thousands of feet, contacting far more rock than a vertical well. Combined with hydraulic fracturing, this is what made shale plays like the Permian, the Bakken, and the SCOOP/STACK economic.
Horizontal wells are usually drilled from pooled or spaced units, so many separate mineral owners share one well. That makes your decimal interest a function of where your acreage sits relative to the unit, not just the wellbore.
The sideways portion is the lateral, and its length is a major driver of how much a well can produce and what your royalty might be worth.