Answer:
A glacial period is an interval of time within an ice age marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate between glacial periods. The Last Glacial Period ended approximately 15,000 years ago. The current interglacial is the Holocene.
-Wikipedia (reworded a little but u can do more if you'd like)
Shorter version:
"A period in the earth's history when polar and mountain ice sheets were unusually extensive across the earth's surface."
-Oxford Dictionary
I hope this helps :)