A very large, unspecified number of things.
Squillions is a fun and informal way to talk about a huge amount of something.
Examples:
There are squillions of stars in the sky.
I have squillions of toys in my room.
She has squillions of stickers on her notebook.
I ate squillions of cookies at the party.
I have squillions of friends.
There are squillions of grains of sand on the beach.