FSR is AMD's name for their software upscaling technology. I guess Sony went and wrote their own upscaler because as someone above pointed out PS5 technically already had FSR, but similar to Nvidia DLSS, it's all the same idea : render a small frame image (like 720/1080) at higher quality detail and use AI to blow the frame up to 4k before it reaches the display.
45% faster is kinda meager considering it's 4 years newer. Hopefully it's based on Radeon 7000 series (or maybe 8k) so it's raytracing is actually useful.