I tried to google it and it left me very confused.
In: 306
Sail ships have a [big fin](https://keyassets.timeincuk.net/inspirewp/live/wp-content/uploads/sites/21/2015/01/Keel-safety-tips-Keels-Sep14.jpg) underneath called a keel, and the purpose of it is to prevent the ship from being pushed sideways by the wind.
So then, the sails aren’t [like this](https://cdn.boatinternational.com/files/2021/06/dd062130-d346-11eb-922c-a95d91958631-Maltese-Falcon-Superyachts-Monaco-3.jpg) where the wind pushes the ship from behind, they are [like this](https://photo-assets.superyachttimes.com/photo/183202/image/large-19e53079b60be7d27fbca4b11c064372.jpg), where the wind “bounces off” the sail and gets redirected. The effect is that the total force pushing on the boat has a different direction than the wind direction.
So [here’s an image](https://www.kavas.com/media/wysiwyg/sailorsguide/how-sails-work.jpg), the wind is blowing straight down from the top, but as you can see it gets deflected by the sail, so the force on the sail is the yellow arrow towards the lower LEFT corner of the screen. And then the KEEL completely prevents the downward portion of that force from moving the ship, so the only “portion” of the force that’s left is the red force moving the ship forward.
So because ships can [angle their sails](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Points_of_sail–English.jpg/300px-Points_of_sail–English.jpg) to deflect the wind as it suits them, they can pretty much go even at relatively steep angles against the wind. Not DIRECTLY against the wind though, for that they actually have to zig-zag left and right so that their angle vs. the wind is outside that red cone. This zig-zag maneuver is called tacking.
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