When the wind blows, the boat wants to move forward and sideways.  The keel prevents the boat from going sideways, so it goes (hopefully) forwards : This is easy to understand when the wind is behind the boat: But is more difficult with the wind in front : The  angle of the sails is important. They must be set at the right angle to the wind to generate the most lift. The  action of adjusting the sails is called  trimming  them. But a boat cannot sail directly into the wind. If the wind  gets too far forward (in front) of the boat it will not generate enough ‘lift’ and the boat will stop.  The relationship of a boat to the direction the wind is blowing is called the ‘point of sail’ :  A boat cannot sail directly into the wind, if it does it will be  in irons  - it will stop moving. A modern boat can  sail at an angle of about 45° to the wind, any closer and it will lose speed. The closest it can go is a  beat  when the boat would be said to be  close hauled. If the wind is coming from the side of the boat it is  reaching.  From 90° to the axis of the boat it is on a beam  reach . If the wind is forward of this it’s a  close reach  and aft of this a  broad reach . If the wind is behind the  boat it is  running  and if it is directly behind the boat it is on a  dead run . Downwind  is sailing “with the wind” - in the direction the wind is blowing.  Upwind  is against the wind.  Downwind and upwind also include anything in that direction from your boat (e.g. Crew : “Skipper, can you  see that bloody great rock downwind of us?” - Skipper : “What rock?”).  Sailing downwind is easy. You hang the sails out and go!  Sailing into the Wind Points of sail Sailing Basics Wind Figure 4 Figure 3 Wind “In Irons” Beating Reaching  Running Head to Wind  Close-hauled  Figure5 Down Wind Up Wind You can think of the wind being like a hill. Upwind is uphill from you and will take a lot of work to get  there. Downwind is downhill and is much easier to get to.