Clarify 1st arg of load()
RELNOTES: None
@@ -23,6 +23,11 @@ imported by using additional arguments to the call to `load`. Arguments must
be string literals (no variable) and `load` statements must appear at
top-level, i.e. they cannot be in a function body.
+The first argument of `load` is a [label](https://docs.bazel.build/versions/master/build-ref.html#labels)
+identifying a `.bzl` file. If it is a relative label, it is resolved with
+respect to the package (not directory) containing the current `.bzl` file.
+Relative labels in `load` statements should use a leading `:`.
+
`load` also supports aliases, i.e. you can assign different names to the
imported symbols.
