Web part zone
The Web part zone web part provides a web part zone that can be used to group multiple web parts or assign additional formatting to them. The zone may also be configured to display its content at a fixed location on the screen that moves along with page scrolling.
More information about layout web parts in Kentico CMS can be found in Kentico CMS Developer's Guide -> Development -> Web parts -> Layout web parts.
Web part zone
This web part serves mainly to group several web parts on the page or provide widget zone in specific location of the page.
Always visible zone
It also supports the always visible functionality that can position the zone to a fixed location on the window. This one is positioned to the middle right.