Final answer:
The underground economy, or shadow economy, refers to an unregulated market that operates outside of governance and human protections. It involves undocumented and untaxed activities, often involving illegal trade. It exists worldwide and plays a significant role in nonagricultural work in many countries.
Step-by-step explanation:
The underground economy, also known as the shadow economy, is an unregulated market that operates outside of governance, regulatory systems, and human protections. It is characterized by activities that are undocumented, untaxed, and often involve illegal trade. The underground economy exists globally and includes various types of jobs, such as unlicensed cab drivers, piecework seamstresses, and street vendors. It is estimated that the underground economy accounts for a significant portion of nonagricultural work in many countries.