Period
Period explained in an easy to understand way:
Imagine trying to organize a bookshelf where each book is a different genre but organized by the height of the book rather than the content. Just like how you arrange these books from left to right by height, a period on the periodic table arranges elements in a horizontal row, ordered by increasing atomic number. Each element in a period is like a book on your shelf, differing in properties but aligned by a systematic increase in atomic structure, much like your books are organized by their physical size rather than their story content.
Practice Version
Period: A unit of geologic time that lasts tens of millions of years, it is longer than an epoch but shorter than an era. Periods are segments of time in Earth's history used by scientists to organize geologic events.