A FPGA Mezzanine Card is a type of circuit board that can be added to a computer to add extra capabilities. It looks like a card that fits inside the computer, and it has a special type of semiconductor - called an FPGA - that can be used to add extra features like computing power, storage, and special functions. FPGA Mezzanine Cards make computers more powerful, and can be used to do things like powering AI or machine learning.