What attaching a package puts on the search path with it, in the order R attaches them.
Readonly
what it Depends on: R attaches these first, so they end up below it
Depends
the core set a MetaPackageCores|meta-package attaches from its .onAttach hook, above it
.onAttach
What attaching a package puts on the search path with it, in the order R attaches them.