Search allows you to search your contacts by keyword.

Search contacts based on first name, last name, organisation, job title, department, notes, phone number, or email address.

Doesn't the iPhone already have contact searching? Yes, however many people find the algorithm too basic for their needs. Search adds more sophisticated search algorithms, including quick search, which minimizes the keystrokes needed to find a contact:

Type the first letter of the persons first then start typing their last name. For example, if you were searching for Layton Duncan, you can just type 'ldu' Using this algorithm you can find contacts quickly with minimum key strokes.

Search also searches through more fields that the built in search function. It delves into phone numbers, email addresses, contact notes, and job title.