Lewis Acid-Base Theory is a concept in chemistry that expands the definition of acids and bases beyond the traditional Brønsted-Lowry theory. According to this theory, a Lewis acid is any substance that can accept an electron pair, while a Lewis base is any substance that can donate an electron pair. This allows for a broader range of chemical reactions to be classified as acid-base interactions. In this framework, the formation of a Lewis acid-base complex occurs when a Lewis acid and a Lewis base interact, resulting in the sharing of electron pairs. This theory is particularly useful in understanding reactions in coordination chemistry and organic chemistry, where electron pair transfer is crucial.