What means by treat?

When I ventured up to the attic to clear out the broken camera equipment, the mildewed books, the broken projector and fading film, and the Easter baskets left over from my childhood, I found that a friendly family of mice
had taken up residence and had left, like the Easter Bunny, “treats”.

I don't quite understand the traditions in Easter,and is there anybody who can tell me something about the last sentence of the passage?
Many thanks!