From the Nobel press release:
On many markets, buyers and sellers do not always make contact with one another immediately. This concerns, for example, employers who are looking for employees and workers who are trying to find jobs. Since the search process requires time and resources, it creates frictions in the market. On such search markets, the demands of some buyers will not be met, while some sellers cannot sell as much as they would wish. Simultaneously, there are both job vacancies and unemployment on the labor market.
This year’s three Laureates have formulated a theoretical framework for search markets…The Laureates’ models help us understand the ways in which unemployment, job vacancies, and wages are affected by regulation and economic policy. This may refer to benefit levels in unemployment insurance or rules in regard to hiring and firing. One conclusion is that more generous unemployment benefits give rise to higher unemployment and longer search times.