They load lightning fast and focus in on a single benefit with a strong call to action, so people can decide it two seconds if they want to continue following the path they point to. Otherwise, you lost them!
Lots of people use services to create them, but I would rather create my own and maintain full control. I also earn better commission than the services offer me. If you have a free account, it is probably extremely restricted until you upgrade.
For an example of mine Click Here
I can show you how to create these in a few minutes.
(or do them for you free)