What is the meaning of [If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck]

“It is usually safe to identify somebody as a particular type of person when his or her appearance, behavior, and words all point to the same conclusion.”,Martin H. Manser (2007). The Facts on File Dictionary of Proverbs. Infobase Publishing. ISBN 978-0-8160-6673-5.