Sounds pretty normal. For a single pole switch, line and load are interchangeable. Without a neutral in the box (actually I lied - there is a neutral in the box, but you can just ignore it; tuck it deep in the back of the box), there's nothing to confuse or do wrong. Ground to ground. One of the black lines to one of the gold-colored posts, the other black line to the other post (you'll want a pigtail for the line that is two twisted-together black wires). Differentiating line vs load only matters if you're using a smart switch or 3-way switch (two switches control one light).