People who are fully sighted read printed materials and use a computer by using their vision. Persons who are blind or visually impaired rely on a device, computer program, or combination of the two, to present the information in a modified or alternative format. These devices and computer programs are commonly referred to as assistive technology.
Assistive technology is nothing mysterious or magical.
It is simply an alternative means to assist with reading and writing information. If you think about it, that same definition could be used to describe the purpose and function of a computer for all persons. If so, you have used technology which was originally developed for persons with disabilities. Thus, you've used or are using assistive technology. Assistive technology that assists a person in reading information will produce the information in a larger form, speak the information audibly via synthesized voice, or produce the information in Braille.