changed the grammar used to define Factory pattern

pages/Design-Patterns.md

@@ -14,7 +14,7 @@ your code easier to manage and easier for others to understand.
 
 ## Factory
 
-One of the most commonly used design patterns is the factory pattern. This is a pattern is simply a class that creates
+One of the most commonly used design patterns is the factory pattern. In this pattern, a class simply creates
 the object you want to use. Consider the following example of the factory pattern:
 
 {% highlight php %}