Google announces 2019 Core Update on September 24th. In general, Core updates impact how Google ranks websites.
Also, core updates is all about how Google determines what is the most relevant web page for particular query.
Google also given us advice what to do if your website hit negatively by this core update
One more thing is that, Google started transforming the core update names with month and year from this update. This is to avoid the confusion over previous updates.