Oxides are chemical compounds that consist of oxygen combined with another element. They can be found in various forms, such as solids, liquids, or gases, and play important roles in nature and industry. For example, water is a well-known oxide, made of hydrogen and oxygen, while rust is an oxide of iron that forms when iron reacts with oxygen in the presence of moisture. Oxides can be classified into two main categories: metal oxides and non-metal oxides. Metal oxides, like zinc oxide, are often basic and can react with acids, while non-metal oxides, such as carbon dioxide, are typically acidic. Understanding oxides is essential in fields like chemistry, environmental science, and materials engineering.