Typically we see ARM hardware inside these USB thumb drive-sized devices, though obviously Intel's implementation sports a x86 foundation inside and is capable of running Windows 8.1.
More specifically, the stick wields a Bay Trail-T based Atom Z3735F processor, which is a quad-core part clocked at 1.33GHz (1.83GHz Burst) with 2MB of L2 cache. It also boasts up to 2GB of RAM, 16GB or 32GB of eMMC storage space, a microSD card slot, two micro USB 2.0 ports, 802.11n Wi-Fi, Bluetooth 4.0, and of course HDMI output. There's also a power button.
On the software side, the dongle can run Windows 8.1, Android, or Linux, according to the product description page on Ali Express. The Chinese e-tailer is selling the stick for $110 plus $14.56 shipping to the U.S., though it's not clear if that's for the 16GB or 32GB model, nor whether it has 1GB or 2GB of RAM. Either way, it's being pitched as a fully functional PC.
We're starting to see more and more HDMI sticks emerge. Google helped popularize the form factor with its affordable Chromecast dongle, though Google is far from the only player. Roku comes to mind, as does Matchstick, the first HDMI stick based on Firefox OS (and currently on Kickstarter) by Mozilla.