The lasers are guides of what you're measuring. The best is the circle laser. All infrareds are measuring a spot that gets larger as you move the infrared further away from what you're measuring. The circle laser shows you the exact spot you're measuring. Dual lasers will give you a rough picture of the spot you're measuring. A single laser shows a single point of what you're measuring. Typically it's one point at the bottom of the spot you're measuring.

It tells you one size of spot you're measuring at a given distance. A 12:1 optic range means you're measuring a 1-inch spot at 12 inches. As you move away that spot grows. So a 12:1 optic range at 24 inches away would be reading a 2-inch spot. Larger optic ranges, like 30:1 will read a tighter spot at a further distance, making them ideal for hard to reach areas like ceiling vents or super-hot pizza ovens.

No. Infrared technology measures just the surface temperature. We do have a few combo units which include a jack for a probe or an integrated probe. Thermapen IR has infrared sensor as well as internal probe.

Emissivity is a measure of the efficiency in which a surface emits thermal energy. Each surface has a different emissivity value. Infrared thermometers either have a set emissivity if they're for specific purposes (like our food safety infrared)or adjustable. You can refer to our emissivity table for values of different materials: https://www.thermoworks.com/emissivity-table/