Using AXL and UpdateLine, is there an implicit register done?

Our customer mentioned that through the gui, when they change a line - they must then register it.  What api does this?  Or does the UpdateLine implicity do this for us?

If all you want to do is update information about a line, then updateLine is all you need.  I'm not sure what you mean by "register".  If by "register" you mean associate the line with a phone, then you would specify line information in an addPhone or updatePhone AXL call. 

Maybe it is Reset?  Do you have to reset the line and/or phone after you update something on it to get the new setting to take affect?

Depending on what you change, yes, you need to do an applyPhone and sometimes a resetPhone and a restartPhone. 

Is there any documentation with an explanation of what these do?  I am in the Cisco Unified CM AXL Schema Reference to get formats and such…but there is no descriptions of what they do or when to use them.

There is no detailed documentation on what the AXL calls do.  They're pretty self-explanatory.  It also helps to use SoapUI to examine the AXL API. applyPhone is the equivalent to clicking "Apply Config" when you are editing a phone in CUCM web administration.  resetPhone is the same as clicking "Reset" and restartPhone is the same as clicking "Restart" from the "Reset" dialog box.