Search was initially part of the Storage feature and is now a standalone feature.

In eZ Platform, you find 3 search engines possibilities :

1. Legacy
2. Solr integration
3. ElasticSearch integration

The Search Engines integrations have real search capacities and are not just filtering the results.

In the last version, ElasticSearch is more advanced than Solr : it has Field Filters, Field Sort Clause, Language Analysis.