Simplify the following text for a Grade 6 native English-speaking person.
Original: The Silurian is the period that extends from the end of the Ordovician , about 444 million years ago to the beginning of the Devonian period , about 416 mya .
Simplified: The Silurian is a geologic period and system that extends from the end of the Ordovician Period , about 443.7 Â 1.5 Mya ( million years ago ) , to the beginning of the Devonian Period , about 416.0 Â 2.8 Mya .