Humbuckers are a style of electric guitar pickup that uses two sets of coils arranged in a way to cancel out noise. This arrangement allowed for higher-gain output pickups without the associated hum that typically comes with single-coil pickups. Additionally, humbuckers also tend to have a thicker and warmer tone, and are typically associated with heavier-sounding genres of music like rock, blues, and heavy metal.
The term "open-coil" refers to the design of the pickup. These types of humbuckers have the coils visible, as opposed to being covered or enclosed in any way, which can produce a slightly brighter and more clear sound.
So, having two open-coil humbuckers on your electric guitar is associated with a classic and versatile tone that could suit many genres of rock, blues, and even jazz and metal.