If you are used to SQL databases, you may know that before you can start inserting the data in the database, you need to create a schema, which will describe what your data looks like. Although Elasticsearch is a schema-less search engine and can figure out the data structure on the fly, we think that controlling the structure and thus defining it ourselves is a better way. In the following few pages, you'll see how to create new indices (and how to delete them) and how to create mappings that suit your needs and match your data structure.