Title: Promise Constraint Satisfaction Problem Abstract: What kind of mathematical structure in computational problems allows for efficient algorithms? This fundamental question now has a satisfactory answer for a rather broad class of computational problems, so called fixed-language Constraint Satisfaction Problems (CSPs) - it has turned out that their complexity is captured by a certain specific form of symmetry. I will give examples of CSPs, explain the connection to symmetries, and briefly discuss some of the major results and research directions. The second part will focus on recent developments in one of these directions, the promise CSPs, which include problems such as finding an l-coloring of a k-colorable (hyper-) graph.