README.md in arc-furnace-0.1.14 vs README.md in arc-furnace-0.1.15

@@ -97,10 +97,15 @@
 
 #### Unfolds
 
 An `Unfold` acts as a source, however, takes a source as an input and produces multiple rows for that source as an output.
 A common case for this is splitting rows into multiple rows depending upon their keys. The `BlockTransform` and associated
-sugar in the `unfold` method of `Pipeline` make this fiarly easy (see `pipeline_spec.rb`).
+sugar in the `unfold` method of `Pipeline` make this fairly easy (see `pipeline_spec.rb`).
+
+#### Observers
+
+An `Observer` acts as a source and takes a source as an input and serves as a pass-through for a stream. Observers
+are used to observe the data stream--record data for use elsewhere.
 
 #### Sinks
 
 Each `Pipeline` has a single sink. Pipelines must produce data somewhere, and that data goes to a sink. Sinks
 subscribe to the `#row(hash)` interace--each output row is passed to this method for handling.