diff --git a/website/docs/configuration/expressions.html.md b/website/docs/configuration/expressions.html.md
index 064fd5e54..74310c8ec 100644
--- a/website/docs/configuration/expressions.html.md
+++ b/website/docs/configuration/expressions.html.md
@@ -673,12 +673,23 @@ Since the `for_each` argument accepts any collection or structural value,
 you can use a `for` expression or splat expression to transform an existing
 collection.
 
+The iterator object (`ingress` in the example above) has two attributes:
+
+* `key` is the map key or list element index for the current element. If the
+  `for_each` exression produces a _set_ value then `key` is identical to
+  `value` and should not be used.
+* `value` is the value of the current element.
+
 A `dynamic` block can only generate arguments that belong to the resource type,
 data source, provider or provisioner being configured. It is _not_ possible
 to generate meta-argument blocks such as `lifecycle` and `provisioner`
 blocks, since Terraform must process these before it is safe to evaluate
 expressions.
 
+If you need to iterate over combinations of values from multiple collections,
+use [`setproduct`](./functions/setproduct.html) to create a single collection
+containing all of the combinations.
+
 ### Best Practices for `dynamic` Blocks
 
 Overuse of `dynamic` blocks can make configuration hard to read and maintain, so