A whitebox is a lettable space with a minimally finished interior.
Usually it contains ceilings, lighting, plumbing, heating and cooling (HVAC), interior walls (painted or unpainted), electrical outlets, elevators, rest rooms, and a concrete floor.
A whitebox is considered ready to lease and can be thought of as a “blank canvas”.
The tenant installation will provide carpets, tiling, cabling, wallpaper, fixtures etc.
In many cases, the landlord (the lessor) will offer financial incentives in the form of a tenant installation allowance (TIA). This pays for or can be used to offset the cost of any improvements necessary for the tenant (the lessee) to occupy the building itself.