Somatic mutations refer to changes in DNA that occur within body cells, as opposed to reproductive or germ cells. These mutations can happen at any time during an individual's life and are not passed on to their offspring. They often result from errors made when the cell is replicating its genetic material (DNA) or due to exposure to environmental factors such as radiation, chemicals or viruses that cause damage to DNA. These mutations can lead to various health issues including cancer and other diseases.