When filling out form 4797 for the sale of rental property, what go into line 2?

I assume it is the total depreciation Ive taken on the property since I purchase it.  If so, by taking depreciation on a rental property, I'm just delaying being taxed on the depreciation amount until I sell.   Is there a gain for taking the depreciation?  Do I pay less on a capital gain then I would pay on my regular tax bracket.