They are not the same no matter how much they coincide in some aspects and we will try to explain it with some examples.
The Usability ensures that customers, to seeing the window of our shop, be tempted to come to watch our items and end up going through box. The accessibility is responsible for removing the front steps if the customer uses crutches or mom comes with a baby stroller.
We are aware that comparisons are odious and sometimes idle, but the example allows us to appreciate how Usability and accessibility are necessary to favor the transit of customers through our site. Thus, our page can be very usable, but not accessible at all (the mother does not enter) and vice versa. The mother and five friends enter, all with a cart, but no purchases.
In practice, both concepts are confused and equated into one with a disastrous result: Usability or accessibility is not achieved. As much as some factors coincide, for example the use or not of certain colors, the truth is that the usability needs of people with disabilities are not the same as in people without disabilities.
But it is not about making two versions of the same page or of the same store. The appropriate thing is to ensure its usability and later, on that basis, add the elements that facilitate its accessibility.
Needless to say, and I apologize to those affected, that a good part of the pages on the Internet lack any usability, and about their accessibility better not to mention.
