When replacing worn shocks absorbers, you can either replace the entire strut assembly or simply replace solely the shock. Monroe Shocks and Struts has supplied quick struts and naked struts for comparison in this video. Using the quick strut, installation is faster and easier as you do not have to use a spring compression tool and disassemble the old strut.
Monroe - http://www.monroe.com
When To Replace Struts - http://youtu.be/HL7K5F-XsZs
Installing New Struts - http://youtu.be/VUHEymwb-tk
This post brought to you by Monroe® Shocks and Struts. All opinions are 100% mine.