<p>This paper reviews the existing definitions of grid resilience and its metrics at distribution and transmission levels, while investigating resilience requirements and assessment methods. The paper also focuses on methods to enhance grid resilience through planning and real-time control strategies. It has been found in the review that, to date, there have not been a commonly agreed definition and methods to assess power system resilience and that it is essential that the grid operators have coordinated solutions addressing the power system resilience from generation to transmission, distribution and local systems and distributed energy resources. Main suggestions for future research on grid resilience could include development of resilience metrics and resilience-readiness assessment framework, development of methods to integrate resilience into the long-term planning of the power systems, development of a co-simulation of interdependent systems, and most importantly, real-life demonstrations and validations of resilience solutions.</p>