Command Line Tools for Xcode ってなに?

Command Line Tools for Xcode 11.0

The Command Line Tools enable UNIX-style development via Terminal by installing command line developer tools, as well as macOS SDK frameworks and headers. Many useful tools are included, such as the Apple LLVM compiler, linker, and Make. If you use Xcode, these tools are also embedded within the Xcode IDE.

macOS SDK Frameworks