There's a label on the back as well with details. The front label is a billboard, designed to get your attention and take advantage of brand loyalty, so yes - you are expected to know it's detergent, and they are happy to handle the crazy rare edge-case person who does not recognize the brand. I suspect they also expect the supermarket you buy it at to have it in the "laundry detergents" section, likely with labels as well, so it's not necessary on the front label.
There's a laundry section, with detergent, fabric softeners, and other laundry-related products. I don't think the backs generally say what the product is, and even if they do, that's not very useful. And as I said, most laundry brands have non-detergent products. Not labeling detergent as detergent trains people to not look for the "detergent" label, which means that they don't notice when they're buying fabric softener or another product.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.