This document summarizes a review paper on grid computing. It begins with an introduction to grid computing, describing it as a system that combines distributed computing resources to solve large-scale computational problems. It then discusses the layered grid architecture, including the fabric, connectivity, resource, and collective layers. Next, it outlines different types of grids like computational, data, service, and collaborative grids. It proceeds to examine challenges in grid computing such as security, resource discovery, and heterogeneity. It also describes characteristics of grids like their heterogeneous and user-centric nature. The document concludes by covering topics like grid resource management and security issues in grids.