The AMD Radeon 660M is an integrated GPU in the entry level Ryzen 6000 series for laptops (Rembrandt, e.g. Ryzen 5 6600U). The GPU is based on the RDNA2 architecture and has 6 of the 12 CUs (= 384 shaders) clocked at up to 1,900 MHz (depending on the CPU model). The 680M and 660M iGPUs are the first integrated graphics card with hardware raytracing support, although the performance is too slow to use it in current games.
Due to the halved CU count and lower core clock, the Radeon 660M is clearly slower than the Radeon 680M and most likely only on par with the old Radeon Vega 8 iGPUs.
Thanks to the modern 6nm process and clever power-saving features, the power consumption is comparatively low (according to AMD), so the graphics card can also be used for slim and light notebooks (depending on the CPU model).