Y-DNA refers to the genetic material found on the Y chromosome, which is passed from father to son. This type of DNA is useful for tracing paternal lineage and understanding family ancestry. Since only males have a Y chromosome, Y-DNA testing can reveal information about a person's direct male ancestors and their migration patterns over generations. Y-DNA testing is often used in genealogical research and can help individuals connect with distant relatives. It can also provide insights into ancient human populations and their movements, contributing to studies in fields like anthropology and population genetics.