Information retrieval (IR) is the activity of obtaining information resources relevant to an information need from a collection of information resources (documents).
Searches can be based on full-text or other content-based indexing. Information retrieval is the science of searching for information in a document, searching for documents themselves, and also searching for metadata that describes data, and for databases of texts, images or sounds.
Automated information retrieval systems are used to reduce what has been called information overload. Many universities and public libraries use IR systems to provide access to books, journals, and other documents. Web search engines are the most visible IR applications.
Since I am specialized in the Open Source Lucene Ecosystem. my services are limited to Solr, Lucene. Nutch, Tika, and Hadoop.