Pure water is water that has been treated physically or chemically to remove most of the impurities and dissolved substances, but may still contain traces of dissolved substances. Deionized water, on the other hand, removes ions from the water through ion exchange technology, leaving it virtually free of dissolved substances. While pure water can be obtained by distillation, reverse osmosis, and other methods, deionized water needs to be treated with equipment such as ion exchange resins or ionization membranes. Pure water is commonly used in experiments and production processes in laboratories, medical and pharmaceutical fields, while deionized water is more commonly used in electronics, semiconductors, photovoltaics and other industrial fields with high purity requirements.