Sometimes travel dates aren't set in stone. If your preferred travel dates have some wiggle room, flexible dates will show you flights up to 3 days before/after your preferred dates. That way, you can see if leaving a day or two earlier will find you a better deal. You can also select the flexible "weekend" or "month" search options to widen your search range and find the cheapest price that works for you.
A simple flight search at https://www.kayak.com/flights scans for prices on hundreds of travel sites in seconds. We gather flight deals from across the web and put them in one place. Then on the search results page you can use various filters to compare options for the same flight and easily choose the best flight deal from all of the deals coming straight from the travel sites to your screen, with no extra fee from KAYAK.