The given name (the personal name that comes after the family name), i.e. a person's first name.
あなたの下の名前は何ですか？
What is your given name?
申込書には下の名前をローマ字で記入してください。
Please write your given name in Roman letters on the application form.
友達同士では、苗字ではなく下の名前で呼び合うことが多い。
Among friends, people often call each other by their given names rather than family names.