What is it?
Accessibility in the IT world is usually referred to as making sure people with disabilities can use digital products. It is a bit more than that. Accessible design (or development for that matter) makes sure everyone can use the same products and no information is inaccessible to any one user. In practice this does mean that you pay special attention to how people with disabilities will use the products, simply because there are some challenges to overcome in that area.
How do we do it?
Two of the most common areas design must consider are visual- and auditory impairments. How we design can greatly impact how users with these impairments experience the digital world. Simple tweaks like adding an icon to a red error message so people with color blindness can also spot the difference can make a big difference.
What we do is we try to imagine how these different groups of people experience things and accommodate for it in the designs we make. We also follow the WCAG 2.1 guidelines. These are international standards regarding accessibility.