While browsing the web in Safari, two bars typically appear in the app: the navigation bar (top) and the toolbar (bottom). As you scroll through a page, on the other hand, the toolbar disappears and the navigation bar shrinks to conserve vertical space.
There are other modes you can use in Safari to complement the web browsing experience, such as full screen mode in landscape orientation and Reader mode in either orientation, but if you’ve ever wished Safari would just use either mode automatically for every page you visit, then you’re going to love using a new free jailbreak tweak called SafaReaderFullScroll by CydiaGeek.