A loan for housing in Norway is a loan against a mortgage. In other words, a mortgage means that you take money plus interest from the bank (the loan), and the guarantee for the bank to get the money back is that you pledge your property, e.g. your house, flat or land.
A mortgage is usually seen as a loan to buy a house. In this case, the pledge is the flat or house purchased with the money received from the bank. However, this is only one, albeit the most common, type of mortgage.
More about mortgages