Search is a core capability of SharePoint that enables end-users to search the contents and metadata of documents, list items, and pages in a SharePoint site. This tag should be used for questions specifically on search capabilities or incorporating search capabilities into developed solutions.
SharePoint search is a built-in native capability with extensive customization capabilities and can be configured to meet specific business needs or be incorporated into fully custom solutions.
SharePoint Search includes a client object model (CSOM) that enables access to most of the Query object model functionality for online, on-premises, and mobile development. You can use the Search CSOM to create client applications that run on a machine that does not have SharePoint installed to return SharePoint search results.
The Search CSOM includes a Microsoft .NET Framework managed client object model and JavaScript object model, and it is built on SharePoint. First, client code accesses the SharePoint CSOM. Then, client code accesses the Search CSOM.
For more specifics on SharePoint search capabilities, see https://learn.microsoft.com/en-us/sharepoint/dev/general-development/search-in-sharepoint.