How do you stop programs from running in background?

[masetas]

On WinMo which ran on the tp2 you had to constantly close programs or do a reset to have as much free memory as possible so it can run some what smooth but Android is build different there is no need for task killers really because even if you had 20 programs open you still would be able to multitask without any lag since android will automatically temporarily close any programs that are not being used in the moment but are still open so it can free up the memory it needs to run smooth when you use an advanced task killer it closes everything some times it closes things that need to be open so other things could run properly..... thats just what i know correct me if im wrong

also you dont need to install any third party task killers since the phone comes with a task manager that is easily accessible and closes all programs