Amazon Fire TV and FireTV Stick are Android based (FireOS fork) TV Set Top Box devices. Based on Android 5.1 they support applications and games via HDMI and remote/controller.
The Amazon Fire TV family of devices currently run Fire OS 5, which is based on Android 5.1 (Lollipop, API level 22). The original FireTV and FireTV Stick devices ran Fire OS 3 (Jelly Bean, API level 17), but with the release of the second generation Fire TV the firmware was updated with native support for Android TV and the v17 Leanback library.
First generation FireTV and FireTV Stick support 720p and 1080p output. Second generation FireTV supports 720p, 1080p and 4K/HEVC output. All devices have HDMI connections, First Gen FireTV has TOSLINK audio, First and Second Gen FireTV have Ethernet and all three devices support WiFi