Your grandmother is your mom or dad's mother. In many traditional cultures, a grandmother lives with her adult child's family and helps raise her grandchildren.
Everyone has two biological grandmothers, maternal (your mother's mother) and paternal (your father's mother). If you're lucky, your grandmother is someone you get to know well. One of the most well-known fictional grandmothers appears in "Little Red Riding Hood," the fairy tale in which a wolf disguises himself as Red Riding Hood's grandmother in an attempt to fool her into being eaten.