Skyscanner.com is probably the best travel website there is

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What is Skyscanner?
Skyscanner is a travel aggregation website, where you can search for flights from one destination to the next or to multiple destinations and the website will give you the results of what airlines and travel agents ( selling on behalf of airlines) offer.

Why is this useful?
Do you want to go from A to B at the lowest cost or in the shortest time either on the most efficient airlines, or the airlines with the fewest stops, or shortest layovers? Or do you want to pay a higher price for a more pleasant flight? Do you want a day layover to explore a new city on the way to your destination? Skyscanner can offer you this and more. To me it is exceptionally useful for booking the cheapest long haul flights with short layovers. It is cheaper to book flights like this through a travel agent on skyscanner than directly with an airline. I guess airlines sell a certain number of tickets through travel agents to price sensitive customers, and if a customer chooses to search for a flight directly on an airline's website the airline knows they are not as price sensitive as the people who use Skyscanner to book cheaper flights.
In addition a lot of airlines still allow you to earn reward points from flights booked through travel agents originating through skyscanner
In my experience oneworld airlines let you do this anyway.

Problems with skyscanner
Some search results display old prices, and if you click the link to the website to buy the flight, the price is no longer available, the travel agent has the same flight available for a higher price. If there are repeat offenders who do this - get to the top of the list for cheapest flights and then have false prices, they should have their place on skyscanner less visible than more honest companies.

How does Skyscanner make money?
Skyscanner is free to use [ you don't pay directly to use skyscanner], but makes money through commission which "comes from either the travel agent or airline when a successful completed booking is made on their site, or on a clickthrough basis" source

Final thoughts
Skyscanner is the most well known travel aggregation website which helps save millions of people per year money, and makes booking flights a fairly straightforward process. Skyscanner is one of the brands I personally admire in terms of how they changed the way I fly.
To my readers are there any better sites like this than Skyscanner or sites you prefer to use?