Developing the technology of your world
When you set out to write speculative fiction, many times you’ll be writing within a world very different from our own. Whether your story is set in ancient times or the far future, your people will still have a set understanding of science and, thus, a certain level of technology.
In order for your readers to feel oriented within your fictional world, it’s important for you to establish what kind of technology they can expect to find within your book. Any deviation from what is “normal” will need to be clarified and used consistently. If your world is mostly medieval but they’ve discovered radio communications, that needs to be made clear and it needs to make sense…otherwise the random radio in the middle of the stone, torch-lit castle will be very jarring.