If you want to compile Qt5 from source, please refer to this page.
When you download precompiled packages from Downloads page, installers will not install any dependencies for you. You need to install them yourself.
Ubuntu/Debian/Mint: To get Qt 5 working here you'll first need build-essentials, which will give you the compilers you'll need(g+). Following that Qt 5 will need some graphics library stuff. Type the following code in the terminal to get the required dependencies respectively:
sudo apt-get install build-essential
By default, Qt also expects XCB and OpenGL drivers to be installed. Usually, many modern distros already do have those packages included by default. If you don't have other OpenGL drivers (supplied by graphics vendor, for example), you can use the mesa package:
sudo apt-get install libx11-xcb-dev libglu1-mesa-dev
MinGW The MinGW package ships with a complete toolchain, including the MinGW compiler.
VS 2010 To compile code in this version you have to download Visual C+ Express 2010. You won't actually use VC++ Express 2010 with Qt, it's just that we need the compiler that comes with it.