A Lewis acid-base complex is formed when a Lewis acid interacts with a Lewis base. A Lewis acid is a substance that can accept an electron pair, while a Lewis base is one that can donate an electron pair. This interaction results in the formation of a coordinate covalent bond, where both electrons in the bond come from the Lewis base. These complexes play a significant role in various chemical reactions, including catalysis and coordination chemistry. They are essential in understanding reaction mechanisms and the behavior of different substances in chemical processes, contributing to fields like organic chemistry and inorganic chemistry.