NNN = Triple Net or Net Net Net
A lease in which the tenant pays all expenses in addition to base rent and is typically responsible all building maintenance.

FS = Full Service
A lease in which the landlord pays for taxes, insurance, maintenance, janitorial, and utilities. The tenant is typically responsible for any increase in any expenses beyond the base year.

IG = Industrial Gross
A lease in which the landlord pays base year expenses such as taxes, insurance, utilities and maintenance. The tenant is typically responsible for any increase in taxes and insurance expenses beyond the base year.