Cluster: A set of Solr nodes operating in coordination with each other via ZooKeeper and managed as a unit.
ZooKeeper: ZooKeeper is an open source project under the Apache Software Foundation. It is a high-performance coordination service for distributed applications. It exposes common services – such as naming, configuration management, synchronization, and group services. For details, please visit https://zookeeper.apache.org/doc/current/index.html.
Collection: One or more Documents grouped together in a single logical index using a single configuration and Schema.
Shard: A logical partition of a single collection. Every shard consists of at least one physical Replica, but there may be multiple Replicas distributed across multiple Nodes for fault tolerance.
Document: A group of fields and their values.
Field: The content to be indexed/searched along with metadata defining how the content should be processed by Solr.
Facet: The arrangement of search results into categories based on indexed terms.
Metadata: Metadata is information about a document, such as its title, author, or location.
Solr Schema (schema.xml): The Solr index Schema defines the fields to be indexed and the type for the field (text, integers, etc.).
SolrConfig (solrconfig.xml): The Apache Solr configuration file. Defines indexing options, RequestHandlers, highlighting, spellchecking and various other configurations. The file, solrconfig.xml, is located in the Solr home conf directory.
Spell Check: The ability to suggest alternative spellings of search terms to a user, as a check against spelling errors causing few or zero results.
Stopwords: Stopwords are generally very small pronouns, conjunctions and prepositions (such as, “the”, “with”, or “and”).
Synonyms: Synonyms generally are terms which are near to each other in meaning and may substitute for one another. In a search engine implementation, synonyms may be abbreviations as well as words, or terms that are not consistently hyphenated. Examples of synonyms in this context would be “Inc.” and “Incorporated” or “iPod” and “i-pod”.