Understanding Down's Syndrome: Mental Issues, Differences, and Daily Life

I don't have down's syndrome, I have questions about the condition!! I've been trying to do research, but everything is very unspecific and only focuses on the big picture. They look different physically and have lower IQ. That's all I can find on the web and that's weird. What are some of the mental issues that people with down's syndrome have? What are some sorts of things that they don't understand? What are some things they do that aren't how other people do those things? Stuff like that. What's a day like living with down's syndrome?