You can implement search as a free-form interface using a third-party search application; or you can use the filtering and querying capabilities of the Content Delivery API to create a query-type interface for searching.
Implementing search using third-party search software To integrate SDL Tridion with your third-party search software, create a custom Module that updates your search index, and add it to your Content Deployer. Although this involves some development effort, it eliminates the need for your search software to crawl your Web site.
Implementing search using filters and queries The Content Delivery API enables you to query the dynamic Component Presentations by metadata. By creating a Web page that calls the API, you can provide visitors of your Web site with an interface that lets them build a query themselves.