“The act of storing data in Elasticsearch is called indexing, but before we can index a document, we need to decide where to store it”
“Relational DB ⇒ Databases ⇒ Tables ⇒ Rows ⇒ Columns Elasticsearch ⇒ Indices ⇒ Types ⇒ Documents ⇒ Fields”
“_index Where the document lives
_type The class of object that the document represents
_id The unique identifier for the document”
Actually, in Elasticsearch, our data is stored and indexed in shards, while an index is just a logical namespace that groups together one or more shards.