Many items over $200 are depreciated over a number of years as "Assets". The Special Depreciation Allowance gives you 50% of that deduction in the first year, then the other 50% is depreciated as usual. [EDIT: Starting September 28th, 2017, the Special Depreciation Allowance has changed to 100%.]
It is an automatic thing. You need to specifically elect OUT of it if you do not want it.
