In hardware, logic is usually categorized into two types: combinational and sequential. Combinational logic is made of logic gates and sequential logic is made of sequential elements that can save states like flipflops. In ASIC design, hardware contains the logic gates required for the specific functionality. In FPGAs the reconfigurability comes from the LUTs which replace the combinational logic gates. I found this introduction about FPGAs interesting: https://www.allaboutcircuits.com/technical-articles/getting-started-with-fpgas-look-up-tables-and-flip-flops/

This slide reminded me that FPGAs are on a spectrum of specialization -- they provide more specialization than CPUs (so energy efficiency gains), but aren't so specialized as ASICs (they allow some programmability via the lookup tables)

How do you program on an FPGA? Is it like CUDA where you can write specialized code in a library that interacts directly with the hardware?