A basic overview of their use is as follows.
On a content switch you configure a virtual host address and port for your application. Then you assign real server addresses to the virtual address in your configuration.
Add a DNS entry for your virtual address and you have a basic server cluster. Clients access the virtual address and the content switch sends the requests to the real servers and vice versa.
This is usually done with web applications. Individual real servers can be taken offline for maintenance or upgrade without impacting client access. Real servers can be added as your client volumes increase.
There many configurable options to tailor the content switch behavior to match your application requirements that you can refer to Cisco's site for.
That is just the basics hope it helps.
