"What are the differences mentally between a DS child and a non-DS child. Are they able to learn the same things?"
Micah started preschool in the fall of 2012 at age 4 knowing the following:
* uppercase letters
* lowercase letters
* phonetics of the letters
* count to 20
This came home from school on Tuesday
There are plenty of kids who start Kindergarten who don't know those things. Micah worked hard to learn those things. But in the right format, those are the things (rote memorization) that are "easy" for him.
Kids with Down syndrome can learn most everything that a "typical" kid can learn. But it might need to be taught differently and it might take them longer to learn it.
The biggest challenge for individuals with Down syndrome is that they tend to be deficient in their short-term ("working") memories. An example: When picking Micah up from school, if you ask him what he did at school, he usually cannot tell you because he truly cannot recall. However, if he is presented with two options, i.e. "Did you learn about apples or balls?" he can usually tell you.
"Executive Functioning" is the umbrella term that describes an ability to adapt and process goal-directed actions. That is a significant weakness in individuals with Down syndrome. Their processing speed tends to be rather slow. This is probably the primary reason why most individuals with Down syndrome are not able to get drivers' licenses.
Micah, like many kids with Down syndrome, learns best when taught with visual and tactile cues. He will likely learn sight reading before phonetic reading. Of course, you and I read sight words and not phonetically, unless faced with a word we haven't seen before. So learning sight words is a practical skill.
Hope that helps shed some light on learning.