How do you list to see what application or task is running?

Then how do you kill the task?

Check the command ps.
Check the command kill.
Get ore info on these by tuping man "command".
Also take a look at:
http://www.linuxnewbie.org/nhf/index.html

type "top"

http://sunsite.dk/linux-newbie/
http://home.att.net/~s.whittlesey/linux_commands.htm

Great resources for newbie looking for a list of linux commands and their function

ps -aux should give you the complete list.