Question [Q] Android third party lockscreens

I have a rooted Samsung Galaxy s3 t-mobile version with cm11 snapshot month 3. I was wondering how do third party lock screens work exactly? Cause for me, i have to keep the app open in order for it to work. Is there anyway to just make it default like the system lockscreen? Or possibly a list of flashable lockscreens and how I would be able to do that?

Thanks!

P.S still kind of new to the whole customizing the android while rooted.