In United States real estate business, normally the landlord, rather than the tenant, is responsible for real estate taxes, maintenance, and insurance. In a "net lease" the tenant or lessee is responsible for paying, in addition to base rent, some or all of the recoverable expenses related to real-estate ownership. As the rent collected under a net lease is net of expenses, the base rent tends to be lower than rent charged under a gross lease.

Net lease types include single net, double net, and triple net leases, depending on the number of items they include. The term "net lease" often being used as a shorthand expression for any of these arrangements. The three most common expenses charged back in this fashion, often called the "three nets", are property taxes, insurance, and maintenance. A triple net lease that includes the three nets is particularly common and is often abbreviated in writing as "NNN lease", but is still pronounced as "triple net lease".