Definitions and clarifications The Library is a technique in which the field is made up of collections of books and periodicals (magazines and newspapers), with the change of times, and the emergence of new information formats, the library has had to adapt to these new forms and resources information, such as online journals, compact discs (CD-ROM) and DVD, microfiche, films (video-tapes, microfilm), audio tapes, etc.. Information Science is the science that is responsible for managing and processing all these information resources and make available, in a simplified and standardized for all users. The electronic world and the library In the world we live in, difficult to find a person who has not sought or created information through electronic means (Internet, CD-rom, dvd, etc.).. The electronic format, especially the compact disc and online databases have revolutionized the world of libraries, so it has been necessary to adapt the traditional card catalogs or cards to new formats, emerging electronic catalogs, being most of these public access (OPAC Online Public Access Catalogs – in English). The concept of collection has been transformed by the emergence of electronic databases, because they need not be physically housed in the library to be accessible to users and also by the volatility of the information they provide.This has been a profound change in the policies of collection of documents (whether in electronic or print) of modern libraries. The functions of the Library today Because of all these electronic changes, we need to redefine the roles of library and information science. In this sense we can make the following definitions: The library can be divided into theoretical and applied. The first section includes topics such as information theory and knowledge management, the study of information needs and how to meet the world, external factors that influence the interpretation of knowledge, and so on.The library applied addresses issues such as development and maintenance of collections, technical processes (acquisitions, cataloging, lending and discard or cleansing) of the collections, interlibrary cooperation, copyright, freedom of information (right of access to information), maintenance, management of the library or information unit, and so on. This area of librarianship is also known as bibliometrics. Along with Informetrics and Bibliometrics is the measure of the potential of documentary data transfer of a library system. Measure the amount of information possible with a search algorithm based on the keywords or descriptors that the reader uses natural language equivalents and synonyms that the system or database used to catalog the documents (terms contained in the categories in For the Wikipedia). It is like the number of references that you download an Internet search engine. The role of the librarian You can understand the role of the librarian as an intermediary between the user and the collection of the library or information center. In order to fulfill its function well, the librarian made called reference interview in order to assist the user of the library in the planning and execution of their search for information.