The top, side, or bottom navigation stays in place while a page is scrolled. In some cases, headings from sub-sections may also become fixed while scrolling and replace or be appended to the existing fixed navigation. Address books are a great example where each alphabetical section (“a”, “b”, “c”, etc.) stick below the top navigation when you scroll past that section header. Photo galleries and file folders tend to utilize this same design pattern. In other cases, menus disappear when scrolling in one direction and become fixed when you scroll in the other direction. Pinterest is a great example of that where the menu disappears at the bottom when scrolling up and appears when scrolling down. This is different from an action bar (a pattern that’s used heavily in Android) to store commonly used app functions.