First, a little history: The Subaru WRX (an acronym for World Rally eXperimental, from the collaboration with British racing team Prodrive in the 1990's), began as what was basically a turbocharged Impreza. Since then, the WRX has evolved into the impressively-specced beast you can buy today at any Subaru dealership.
Starting in 2015, Subaru removed the Impreza branding from both the WRX and STI. The major difference between the 2015 and up models from the 2014 and older vehicles is the use of the FA20F (aka FA20DIT) engine instead of the EJ25 that has been there since 2005. Note that while the earlier Subaru BRZ has an FA20D engine under the hood, this is not the same motor in many respects. While the bore and stroke are identical (86.0mm for both), the compression ratio is lower in the WRX at 10.6:1. It's also fed by direct injection and a twin-scroll Garrett Honeywell GT2295 turbocharger outputting 268bhp @ 5600rpm and 258 lb-ft @ 6700rpm. This VA series WRX comes default with a six-speed manual transmission, with an automatic CVT option with paddle shifters for the Limited and Premium trim levels.
