Accessibility features are accomplished by Semantics library, which handles the semantics tree.
Your app semantics tree is like your apps widgets tree. But instead of containing widgets, it contains semantics nodes the define Accessibility hierarchy passed to the operating system.
So when you need to adjust the accessibility experience, you'll probably just use an API with the word "semantics" in it.
We also need a semantic label to say something clear. For example, the screen reader cannot read 30 km/h as '30 kilometers per hour'. See how it's accomplished in the below examples.
Here are few examples,
Text('30 km/h',
semanticsLabel: '30 Kilometers per hour')
Icon(Icons.library_books,
semanticsLabel: 'Instructions')
Semantics(label: 'What I want to say',
child: MyWidget())
Thanks.