In October of 2017, Insightly introduced new features and a new look.
"Insightly Classic" is the name we've given to the older version of Insightly. All customers have the option of switching to the new Insightly or using Insightly Classic while it's still available — the option is available on your System Settings page.
Some help content has information for both Insightly Classic and the new Insightly. You'll see tabs at the top of those articles allowing you to choose the right content for you.