The easy explanation is noindex means doesn’t get indexed in google. nofollow means google doesn’t give link credit to that pages links.
Examples:
noindex, follow: You could have a page onsite that is noindex (will not show up on google search results page) but google will follow the links out that are on that page.
noindex, nofollw: That page will basically not exist in google and the links on that page will NOT be counted in any way.
index, follow: The page will show up in google and google will let link juice flow from links on that page
index, nofollow: That page will show up in google and the links on that page will NOT be credited with link juice flow.
Yes, most people use the NoFollow and the NoIndex tags together so that a page like a shopping cart page that is dynamically driven isn’t indexed or assigned any PageRank.