Final answer:
A structural hole is an area between dense social networks without ties, indicating weak social connections and social control. Polarization is the increasing gap between low-end and high-end jobs combined with a reduction in middle-level jobs.
Step-by-step explanation:
An area between two or more dense social networks that lacks network ties is a structural hole. This concept highlights the absence of connections in a social network and can indicate weak social ties as well as a lack of social control where society is less able to enforce norms among some groups.
The practice where the differences between low-end and high-end jobs become greater and the number of people in the middle levels decreases is known as polarization. This trend can contribute to economic and social challenges, including increased inequality and the hollowing out of middle-tier jobs.