You may have your own knowledge and experience of accessibility. This could range from little, to a lot. It could be based on your experience, things you have read during your own research, or stuff that you have picked up from colleagues and fellow developers based on their experience and research.
You may not know any people with disabilities or any people who use assistive technology (AT). Much of what you have heard could come from second or third hand information that could either be wrong, or worse, misleading.
You may have downloaded a demo copy of a screen reader and realized that it a very complex piece of software that you can't just hop into and drive off with. Well, not smoothly anyway.
You may have read about certain assistive technology and are trying to picture in your mind how it may work. I am aware that this approach is very difficult. If it is possible for you to gain some hands-on being experience of being with people with disabilities and watch...