Assistive technology means any item, piece of equipment or product system, whether acquired commercially off-the-shelf, modified, or customized, that is used to increase, maintain, or improve the functional capabilities of children with disabilities.Source: Federal Register, August 19, 1991, p. 41272.
https://www.atia.org/at-resources/what-is-at/ from the Assistive Technology Industry Association, Assistive technology (AT): products, equipment, and systems that enhance learning, working, and daily living for persons with disabilities...Assistive technology (AT): products, equipment, and systems that enhance learning, working, and daily living for persons with disabilities.

Assistive Technology (AT) - a generic term that includes assistive, adaptive, and rehabilitative devices and the process used in selecting, locating, and using them. Source: Wiki
Computer accessibility (Accessible computing) – accessibility to computers by all people, regardless of disability or severity of impairment. Source: Wiki
Universal Design – providing greater product usability, especially for people with special needs

Section 508 of the Rehabilitation Act was enacted in 1998 to eliminate barriers in information technology, to make available new opportunities for people with disabilities, and to encourage development of technologies that will help achieve these goals. Source: Wiki
Standards for O/S, web access, computers, telecommunications & video

Medical diagnostic equipment was also addressed in 2010, section 510.

You may want to check out the Rehabilitation Act of 1973 for more specifics https://www.access-board.gov/the-board/laws/rehabilitation-act-of-1973

Cognitive – literacy specific (Reading/Writing)
Visual
Motor & dexterity
Hearing/Listening
Memory/Organization
Learning disabilities (LD)

http://www.assistivetechnology.vcu.edu/files/mt/2/AT_Continuum_Generic10_06... gives complete details on the different levels with examples in the continuum referenced here.

Input devices – keyboards, touch screens, joysticks, trackballs, speech recognition, sip-and-puff, & switches
Output devices – monitors, text-to-speech, screen readers, optical character recognition
Augmentative and Alternative Communication devices – VOCAs, digital speech recorder, etc. (Voice Output Communication Aids (VOCA)/ Speech Generating Devices (SGD) are electronic devices that are able to generate printed and/or spoken text. VOCA aid individuals who are unable to use natural speech to meet all of their communication needs.
Voice Output Communication Aids - Inclusive Design Research Centre
idrc.ocadu.ca/resources/13-resources/technical.../49-voice-output-communica...)

Deafness and hearing loss aids

Braille embossers
On-screen keyboards
Reading (text-to-speech) software
Large print software
TTY/TTD conversion modems

What task does this student need to accomplish in the classroom/lab?
Is this student capable of completing tasks independently without AT?
Is a form of AT currently being used to address this task?
Would use of AT help this student perform the task more easily or efficiently?
Which students need AT?
What kinds of technology are needed?
Who should be involved in making decisions?

See also https://www.atia.org/at-resources/what-is-at/#how-do-you-choose-the-right-a...

Age appropriate software
Cause and effect software
Hand-eye co-ordination skills software
Diagnostic assessment software
Mind mapping software
Study skills software
Symbol-based software
Text-to-speech
Touch typing software
Source: Wiki

In what settings will the AT tool be used (e.g., home, school, work, and/or social settings)?
If the AT tool will be used in more than one place, how portable is it?
How easy is it to learn about and operate?
How reliable is it? Is technical support available?
Does it need to work with other technologies?
Source: Assistive Technology - A Parent’s Guide.