Panda update is to target websites with low-quality content and prevent them from ranking well in search engine results pages(SERP)
Penguin update is to targeting spammy links.
Hummingbird update was designed to improve Google's semantic search capabilities.
This update was special because Google warned website users in advance that it was coming.
In this update, sites that focused on the user experience and distributing high-quality content were rewarded by Google.
This update was designed to learn and predict user behaviors.