Private Mortgage Insurance. Mortgage insurance provided by nongovernment insurers that protects a lender against loss if the borrower defaults.
Translation.
If you can't pay your mortgage, the insurance is there for the lender to recoup their losses.
edit. OP.
you should save 20%
but also...be sure you're buying a house within your means
look at
1. monthly mortgage
2. taxes
3. maintenance
4. HOA(if buying a townhouse/condo or property with a Homeowners Association)
5. all your other monthly bills, eg. avg gas bill for car, avg credit card payment[if you have one], commuting costs, etc
now compare with your monthly take home pay...
if you're just breaking even without being able to squirrel away some money... you may want to look for a cheaper home.
Remember even w. the money you are putting down, owning a home is EXPENSIVE. All things that go wrong with the house, YOU are going to be the one who needs to come out of pocket to fix. Make sure you are making enough to not only cover your monthly mortgage, but also have enough that if something comes up, you have the means financially to fix it. You never know if there will be a problem w. the HVAC, a leak in the roof, plumbing, etc etc...there is much more to owning a house than putting a down payment. Take your time, and don't rush it....
in addition to this.. it's almost a sure thing that you're going to want to do something to change the house when you buy it(unless it's newconstruction)...so you may also want to save up 10K for remodelling...not necessary, but nice to have.