How 2nd liens come into play

[Michael Rosenson]

A newbie question here but I'm having trouble finding this information clearly spelled out somewhere:  What exactly happens when a 2nd lien is established on a property?  Does the borrower now pay two separate mortgage payments each month--one to the 1st lien holder and one to the 2nd lien holder?  Does a 2nd lien holder need permission/approval from a 1st lien holder to take certain actions on the property (for example, things like a loan mod or a foreclosure)?  Anything else worth mentioning on the topic?

Thanks!