The key points， difficulties， and developments of distributed energy resources and energy efficiency as seen at the 21st International Conference on Electricity Distribution（CIRED 2011） are presented. The introduction mainly focuses on four directions， i.e. distributed generation（DG）/distributed energy resource（DER） planning and studies， control of networks with DG/DER， customer side development and DG/DER technology. These topics are hoped to help engineers and researchers widen their vision in related research fields and deepen their understanding of the problems， opportunities， and challenges faced by the distribution system， and finally to promote the R&D and engineering application of smart grid technologies in China.