Here’s how Google described these core updates:
“One way to think of how a core update operates is to imagine you
made a list of the top 100 movies in 2015. A few years later in 2019,
you refresh the list. It’s going to naturally change. Some new and
wonderful movies that never existed before will now be candidates
for inclusion. You might also reassess some films and realize they
deserved a higher place on the list than they had before.”
In March 2018, Google confirmed a broad core algorithm update
had rolled out to benefit “under-rewarded” pages.
A little over a month later, Google released another broad core
algorithm update targeted at content relevance.
Then, another broad core update rolled out in August (sometimes
wrongly and inaccurately referred to as the “Medic” update)
targeting sites with low-quality content.
In March 2019, as an extension of the August 2018 core update,
Google confirmed that a core update (a.k.a., Florida 2) was here and
it was supposed to be a big one.
But, the SEO community felt it was more of a rollback of previous
algorithms.
20 YEARS OF SEO: A BRIEF HISTORY OF SEARCH ENGINE OPTIMIZATION