FPGA
LUT (Lookup Table)
An FPGA primitive that implements any Boolean function of its inputs by storing the truth table in SRAM.
Detailed Explanation
A k-input LUT stores 2^k bits representing all possible output values. The inputs select which bit appears at the output. A 6-input LUT can implement any function of 6 variables.
LUTs are the fundamental logic building blocks in FPGAs. Synthesis maps RTL logic to available LUTs. LUT utilization is a key FPGA resource metric. Some LUTs can alternatively serve as distributed RAM or shift registers.