Lots of people grew up with the vSphere Client, which is also known as the C# client, but VMware has been replacing it with vSphere Web Client (Flash). With 6.5 the new vSphere Client HTML5 was introduced. Now the Flash client is being replaced by this new HTML5 client. In 6.7, HTML5 client is not fully featured and the Flash client is still required for certain workflows, but expect it to be replaced by HTML5 in the near future.
It is nice that we no longer need a separate exe to manage the environment.
Some good overall info on 6.7 here: Introducing vCenter Server 6.7 - VMware vSphere Blog
