I used to think that fidelity and resolution are the same concepts until very recently. However, there is a huge difference between them and it is essential to understand that difference so that you can communicate your ideas effectively.
Fidelity is about the level of details solved and how realistic the concept is, whereas resolution is about the look and how realistic the concept is visualized. On the other hand, a low fidelity / high resolution work might work better than a high fidelity / low resolution in some cases, or vice versa. However, it is important to understand the different roles these 4 quadrants to be able to communicate, test and present ideas effectively.