Entry for QoS (#5993) (#14083)

*  Entry for QoS (#5993)

*  QoSClass terminology

*  QoSClass terminology renamming item

*  QoS definition

*  Review update QoS Class and Grammar

*  dash in glossary id qos-class

content/en/docs/reference/glossary/qos-class.md

@@ -0,0 +1,24 @@
+---
+title: QoS Class
+id: qos-class
+date: 2019-04-15
+full_link: 
+short_description: >
+  QoS Class (Quality of Service Class) provides a way for Kubernetes to classify pods within the cluster into several classes and make decisions about scheduling and eviction.
+
+aka: 
+tags:
+- core-object
+- fundamental
+- architecture
+related:
+ - pod
+
+---
+ QoS Class (Quality of Service Class)) provides a way for Kubernetes to classify Pods within the cluster into several classes and make decisions about scheduling and eviction.
+
+<!--more--> 
+QoS Class of a Pod is set at creation time  based on its compute resources requests and limits settings. QoS classes are used to make decisions about Pods scheduling and eviction.
+Kubernetes can assign one of the following  QoS classes to a Pod: `Guaranteed`, `Burstable` or `BestEffort`.
+
+