Not sure if I understood it correctly. It just means you only pay less this year, but you have to pay again next year. For example you have a capital loss of $4000, and so you pay $1000 instead, but you would have to pay that $3000 again next year. (they probably wouldnt give everyone a free $3000 deduction every year )

Check this site that explains this also, may help you to understand.
http://loopholelewy.com/loopholelewy/13-capital-gains-losses/capital-gains-losses-03-capital-losses-ordinary-losses.htm