user_access( ) - Printing list 'variables' you can plug into? Something I have seen many times, but never fully understood is what exactly to plug into user_access() (Want to get the correct terminology here too, do you just call them variables?). I have seen some basic ones like user_access('manager access'), manager being a made user? Another using user_access('access nodes links'), which I assume is just seeing if they can see/access the tab links on a node. 

If there an easy way to get a common list of what you can plug into user_access()? 

Thanks in advance
You can see all the permissions on the /admin/people/permissions page.