"There is a towel on the shelf."
Translation:Det finns en handduk på hyllan.
To my mind it is as difficult as to feel the difference between "there is" and "it is/this is". Learners can't get the point why and when they should use it. In fact "det finns" is a construction to declare that some material unit is situated somewhere, whereas "det är" points at an object or situation. Pinch me if I'm wrong.) In a real life there will be more freedom in word usage, but here guru want us to be as precise as possible)
Basically, finns is existing and är for being. Exactly what this means can vary, and natives may not always agree on the best option, so there's plenty of overlap in practice.
We also use spatial verbs a lot. These can replace either finns or är, whenever it feels natural to also point out how something is located. So if something or someone is standing, we might use står instead of finns/är. The same goes for sitter and ligger - those are the most common ones by far.
Sorry, bit of a story. My connection seems to have gotten into a strange state yesterday. It wasnt showing any comments and my answer with ligger wasnt accepted (perhaps i had a typo i hadnt noticed). So basically i was trying to ask why ligger didnt work via a bad joke. Which i screwed up royal by typing 'why ligger" instead of 'why finns'. Apologizes for the noise and as always thank you for your tireless contributions to the course.