The 20% deduction will apply to certain "pass-through" business entities. These businesses include partnerships, S-Corps, and sole proprietorships which don't pay taxes at the corporate level but instead pass the income through to their individual owners who pay individual income taxes.
Other tax reform changes that may affect your business include an increase in Section 179 expensing from $510,000 to $1,000,000 and limits on expensing interest from borrowing.