Approximation is a research area in computer science and mathematics that focuses on developing efficient algorithms to approximate solutions to complex optimization problems. These problems are often NP-hard, meaning that it is computationally infeasible to find an exact solution in a reasonable amount of time. Approximation algorithms provide a trade-off between computational efficiency and solution quality by finding solutions that are close to the optimal solution within a certain factor of approximation. Researchers in this field work on developing and analyzing approximation algorithms for a wide range of optimization problems, such as scheduling, routing, clustering, and graph problems.