What are the 8 little Ivies?

Could you please explain what the term "8 Little Ivies" refers to? Are these prestigious universities that are considered to be on par with the Ivy League schools in terms of academics and reputation? If so, which eight institutions make up this group, and what sets them apart from other highly ranked colleges and universities? Are there any notable alumni or achievements associated with the 8 Little Ivies that contribute to their esteemed status?