Difference between Platform SDK and Sailfish SDK

While updating my Sailfish OS Builds in Docker project (because there aren’t enough of these already) I noticed that I build apps using mb2 while the young ones nowadays are talking about sfdk. I also came across this page: SDK ↔ Platform SDK Command Map | Sailfish OS Documentation

Can someone ELI5 me on the difference between the Platform SDK and the Sailfish SDK? Am I ok using mb2 or will it disappear in the near future? Does sfdk use mb2 under the hood?

The Sailfish Platform SDK is a low level tool, which is intended for hardware adaptation developers.

The Sailfish SDK is a higher level tool, which is intended for application developers. It does almost everything that the Sailfish Platform SDK does, and then some: It comes with IDE, emulator, etc.

Using mb2 is fine.

sfdk provides also some functionalities which do not exist in mb2. But some of the functionalities are indeed implemented using mb2 in a virtual environment, running under either VirtualBox or docker.