The element represented by the atomic symbol 'O' is oxygen. It is a non-metal and is essential for life on Earth, as it plays a critical role in respiration for many organisms, including humans. Oxygen is highly reactive, forming compounds with most elements, and is a key component of water (H2O) as well as organic molecules. In nature, oxygen exists primarily as diatomic molecules (O2) and is a necessary element in processes like combustion and photosynthesis.