That last one is "Hammerhead", it's designed to slow you down. It also has a tyre wall in it to make it clear that you're supposed to turn, and that you want to slow down. It's worth noting that is an actual test track, designed to test the ability of different cars, so it isn't actually for high-speed racing.
The official BBC Top Gear website has an interactive map showing you in fairly good detail each of the corners of the map, plus some info about them, and a "Stig's-eye-view" of going around them.
http://www.topgear.com/uk/track-guide