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