Depreciation recapture is the price you pay at sale for all the years of depreciation deductions you took. When you sell a rental, the IRS requires you to pay a flat 25% tax on the total amount of depreciation you claimed (or could have claimed) over your holding period. This is taxed separately from capital gains on the appreciation. So on a property where you claimed $60,000 of depreciation over 10 years and sold at a gain, you owe up to $15,000 in recapture tax on top of any long term capital gains tax on the appreciation. The good news is that recapture is deferrable through a 1031 exchange: if you roll the proceeds into a like kind property, both the capital gains and the recapture are deferred until the next sale (or forever, if you keep exchanging and eventually die with the property in your estate, thanks to the stepped up basis). Understanding recapture is critical when deciding whether to sell, refinance, or exchange a property.
Example
You sell a rental after 12 years. Total depreciation claimed was $78,000. Recapture tax = 78,000 x 0.25 = $19,500 owed separately from capital gains on the appreciation.