The Brønsted-Lowry Theory is a fundamental concept in chemistry that defines acids and bases based on their ability to donate or accept protons (H⁺ ions). According to this theory, an acid is any substance that can donate a proton, while a base is any substance that can accept a proton. This definition broadens the understanding of acid-base reactions beyond just the presence of hydroxide ions. In a Brønsted-Lowry reaction, when an acid donates a proton, it forms its conjugate base, and when a base accepts a proton, it forms its conjugate acid. This relationship helps to explain the behavior of various substances in chemical reactions, making it easier to predict the outcomes of acid-base interactions.