The Search API allows your application to perform Google-like searches over structured data. You can search across several different types of data (plain text, HTML, atom, numbers, dates, and geographic points). Searches return a sorted list of matching text, and you can customize the sorting and presentation of results.
The Google App Engine Search API provides a simple model for indexing and searching data, and displaying the results. Search can query any data, as long as that data is described by a document. You structure data in documents using a number of Field classes to describe different type of text the document contains (plain text, HTML, atom, numbers, dates, and geographic points).
After constructing the document, you can use methods of the Index class to add, remove, or list documents in an index, and also to search an index with a query. The API provides a comprehensive query language that supports numeric and text expressions. The API also allows you to specify query options, such as sort order for results, the number of results returned, and a starting cursor position or offset.
You can use field expressions and snippeted fields to control the presentation and content of search results, and you can use cursors to page through each set of results. Field expressions let you specify which fields to return. Snippeted fields in the QueryOptions class allow you to return an abbreviated snippet of a field instead of its full content.
Matching search results are returned to the application in a SearchResults object. This object includes the number of results found, the actual results returned, and an optional cursor object.
For further information see Google's Search API Documentation.