Sitecore supports both Lucene and Solr search engines. Solr is the default search engine. You must use Solr if you have a scaled environment.
If you use Sitecore Azure PaaS, you can also use Azure Search.
The Lucene provider is available and it can only be used in a standalone environment. Lucene is not supported or recommended in a production environment.
You can move from Lucene to Solr. The LINQ queries remain the same, but there are differences in configuration and so forth that you need to address. You will also have to rebuild indexes. The move is possible, but it is not a trivial task. You should therefore use Solr if you plan to scale your site (have a distributed setup with multiple servers).
If you do move from Lucene to Solr, be aware that Lucene and Solr score search results in slightly different ways (which can look like there is something wrong unless you know this).