This is the 414th most frequent French word.
milliers
"Milliers" means "thousands" in English.
Here, "milliers" is used to indicate a large number of people, giving an estimate without stating an exact number.
Des milliers de personnes se sont rassemblées pour le concert.
Thousands of people gathered for the concert.
In this sentence, "milliers" refers to time, specifically a large number of years, emphasizing the timespan.
On a trouvé des trésors datant de milliers d'années.
Treasures dating back thousands of years were found.
"Milliers" is used to denote a great quantity, in this context referring to numerous flowers.