When you buy a house, if you don't put at least 20% down, you have to pay for private mortgage insurance or PMI. When you get a FHA loan, you get your insurance from the government (get more details about FHA mortgage insurance). With VA (Veterans Affairs) loan and RHS (Rural Housing Service) loans, there is no mortgage insurance requirement.
The benefit of PMI for the home buyer is you get to buy a house before you have the full 20 percent down payment saved. For mortgage lenders, the mortgage insurance protects them if you, the borrower, can't pay the mortgage.
With private loans, once you pay down the mortgage below 20 percent (typically 22%) of the original purchase price, you typically don't have to pay PMI any longer. With government loans, there are many more rules that determine when you can stop paying your government mortgage insurance.
Note: The government mortgage programs continually evolve (down payment requirements, costs at closing, etc) so you should thoroughly your options to find the best financing for your home.