The new Update brings a series of Unity enhancements that include workflow upgrade with Prefab elements, which can now be nested, as well as improvement for programming the render tool, and changes to the .NET platform. Additionally, a new visual effects graph is added that can be previewed.

Changes in short lines:

The .NET scripts have now been changed to .NET 4. Support for the old .NET 3.5 platform will soon be suspended.

Prefab elements now can be nested to increase flexibility. By combining different prefab elements it is possible to create more complex solutions that can be instantiated as one element.

ProBuilder 3D has been updated to version 4.0 which is now supplied as source code and supports improvements to the use of nested prefab elements.

The isometric grid is added that facilitates the process of making a 2D environment.

In addition to these, there are many more changes that add to the improvement of different modules within Unity. You can find more details on this link.