Microgrids are a suitable, reliable and clean solution to integrate distributed generation into the mains grid. Microgrids can present both AC and DC distribution lines. The type of distribution conditions the performance of distribution line and implies different features, advantages and disadvantages in each case. This article analyses, in detail, all this parameters for AC and DC microgrids in order to identify and describe the available alternatives for building and configuring a microgrid. Elements and issues involved in the implementation and development, such as protections, power converters, economic analysis, availability, etc. are discussed and described. This analysis constitutes a tool for selecting a suitable configuration of a microgrid adapted to the needs in each situation. In addition, the article provides a picture of the current situation of microgrids, and identifies and proposes future research lines This workhasbeencarriedoutinsidetheResearchand Education UnitUFI11/16oftheUPV/EHUandsupportedbythe Department ofEducation,UniversitiesandResearchoftheBasque GovernmentwithinthefundforresearchgroupsoftheBasque universitysystemIT394-10andbytheGovernmentoftheBasque Country withintheresearchprogramETORTEKastheproject ENERGIGUNE12(IE12-335). This work has been carried out inside the Research and Education Unit UFI11/16 of the UPV/EHU and supported by the Department of Education, Universities and Research of the Basque Government within the fund for research groups of the Basque university system IT394-10 and by the Government of the Basque Country within the research program ETORTEK as the project ENERGIGUNE12 (IE12-335).