Real estate accounting depreciates buildings that usually appreciate, so net-income understates a property company's economics badly. FFO removes that distortion and is the figure REIT multiples and dividend coverage are quoted against.
It is still not cash available to shareholders, because it ignores the recurring spending needed to keep buildings lettable. adjusted-funds-from-operations makes that correction.
Example: Harbor Row Properties reports $52M of net income, adds back $96M of depreciation and removes an $8M gain on a disposal, giving $140M of FFO, or $3.18 a share.
Related: adjusted-funds-from-operations, dividend-discount-model, net-income, price-to-tangible-book