Update About-Nodes.rst (#3917)

* Update About-Nodes.rst

Co-authored-by: Chris Lalancette <clalancette@gmail.com>
(cherry picked from commit 4c9c035)

source/Concepts/Basic/About-Nodes.rst

@@ -10,7 +10,9 @@ Nodes are typically the unit of computation in a ROS graph; each node should do
 
 Nodes can :doc:`publish <About-Topics>` to named topics to deliver data to other nodes, or :doc:`subscribe <About-Topics>` to named topics to get data from other nodes.
 They can also act as a :doc:`service client <About-Services>` to have another node perform a computation on their behalf, or as a :doc:`service server <About-Services>` to provide functionality to other nodes.
-For long-running computations, a node can act as an :doc:`action client <About-Actions>` to perform it, or as an :doc:`action server <About-Actions>` to have another node perform it.
+For long-running computations, a node can act as an :doc:`action client <About-Actions>` to have another node perform it on their behalf, or as an :doc:`action server <About-Actions>` to provide functionality to other nodes.
 Nodes can provide configurable :doc:`parameters <About-Parameters>` to change behavior during run-time.
 
+Nodes are often a complex combination of publishers, subscribers, service servers, service clients, action servers, and action clients, all at the same time.
+
 Connections between nodes are established through a distributed :doc:`discovery <About-Discovery>` process.