The major categories of disability types are:
Visual - Blindness, low vision, color-blindness
Hearing - Deafness
Motor - Inability to use a mouse, slow response time, limited fine motor control
Cognitive - Learning disabilities, distractibility, inability to remember or focus on large amounts of information
Watch the videos or read the transcripts, to understand the value of web accessibility.
And deafinitely make sure that you caption your videos!