"Additional Insured" or "Additional Interest"?

[Katherine S.]

I'm putting the requirement for renter's insurance in my lease agreements, including $1M for liability.  But I have seen both "additional insured" and "additional interest" as requirements.  What do they mean, what is the difference between the two, and which one should I use?  I want to make sure that I'm notified if a tenant cancels or lets it lapse.