This is an interesting feature. It is called Google Custom Search. This allows you to provide a searchbox on your blog or webpage that only points to a particular site.

We begin by going to the Google custom search site.

http://www.google.com/coop/cse/

We will type in a basic search with some basic search engine keywords related to our site on SAP (its a software package).

We limit the search to just our website.

Now we go to the code area and copy the code.

We then paste it into our WordPress blog, save and then view the searchbox that has been created.

They we will type in a basic search.

Notice how every one of the results is from the http://sapplanning.wordpress.com blog. So we have just basically brought the search power of Google to our one website, and this search box can be imported into any web page or blog.