A Soul Torch is a new type of light that was introduced to Minecraft with the Nether update. They act very much the same way as a regular torch but are pretty much just a color variant, where the fire burns with a turquoise color.
To make a Soul Torch, you will need some charcoal or coal, a stick, and some Soul Soil or Soul Sand. Soul Soil can be found in the sound sand valley biome in the Nether, while Soul Soil can be found at around level 65 in the Nether wastes, at Bastion remnants, or on the surface of soul sand valley.
Place the stick in the center of the crafting table, with the coal or charcoal directly above it, and the Soul Sand or Soul Soil directly below it. One coal/charcoal, stick, and soul sand/soil will produce four Soul Toches.
If you are in the Nether, you should always have some Soul Torches with you, as they will repel piglins, but unlikely normal torches, they will not melt snow or ice. You can also combine a Soul Torch with eight Iron Nuggets to create a Soul Lantern. Just like the Soul Torch, the Soul Lantern will also keep piglins away.