This document summarizes research on improving energy efficiency in data centers through dynamic virtual machine consolidation. It discusses how virtualization allows multiple virtual machines to run on single physical servers, improving resource utilization. Dynamic consolidation techniques migrate virtual machines between servers based on resource usage to minimize the number of active servers and reduce energy costs. The document reviews different server consolidation heuristics that aim to pack virtual machines tightly and turn off underutilized physical machines to reduce energy consumption in cloud data centers.