Binary descriptions:

libc6-arm64-cross: Embedded GNU C Library: Shared libraries (for cross-compiling)
libc6-dbg-arm64-cross: Embedded GNU C Library: detached debugging symbols (for cross-compiling)
libc6-dev-arm64-cross: Embedded GNU C Library: Development Libraries and Header Files (for cross-compiling)
linux-libc-dev-arm64-cross: Linux Kernel Headers for development (for cross-compiling)