One framework for all desktop platforms
Using CrossVcl you focus only on your VCL application and CrossVcl makes it cross-platform.
Win API bridge
CrossVcl provides low-level Windows API bridge to macOS and Linux.
CrossVcl provides native macOS equivalents for almost all standard controls like TEdit, TMemo, TComboBox etc.
TCanvas and TBitmap behave on macOS and Linux like on Windows.
Many custom controls work on macOS and Linux like on Windows unchanged.
CrossVcl requires Embarcadero Delphi 10.2 with macOS development add-on. Enterprise version requires for Linux development.