A chemical reaction is a process in which substances, known as reactants, are transformed into different substances called products. During a chemical reaction, bonds between atoms break and new bonds form, leading to changes in the molecular structure of the involved substances. These reactions can be categorized into various types, including synthesis, decomposition, single replacement, and double replacement reactions. Energy changes often accompany these processes, either released or absorbed, and they play a crucial role in biological processes, industrial applications, and everyday life.