This type of risk include dramatic events such as a strike, plunging revenues, Higher financing cost, Declining profit margins, a natural disaster such as a fire, or something as simple as Management misconduct or slumping sales. Two common sources of unsystematic risk are business risk and financial risk.
However non-systematic risk can be diversified, So instead of investing all your money in one company, you can choose to diversify and invest in 3-4 different companies (ideally from different sectors). When you do so, unsystematic risk is drastically reduced.