A sailing ship does not simply move wherever its crew points it. Wind pushes against sails, while the vessel's underwater shape resists sideways drift and helps convert that force into forward motion. The sails and rigging can be adjusted to work with winds arriving from different angles. A ship could generally make progress across or partly toward the wind, but it could not sail directly into it. To gain ground toward an upwind destination, the crew had to tack in a zigzag pattern.
Different rigs suited different tasks. Square sails worked especially well with favorable winds from behind or across the vessel, while fore-and-aft sails could be more adaptable when sailing closer to the wind. Actual performance depended on hull design, sail condition, loading, and the abilities of the crew. A heavily laden merchant vessel, a small sloop, and a naval ship did not handle in the same way, even when facing similar weather.
Navigation therefore involved choices as much as instruments. A captain might accept a longer route that used reliable winds, avoid dangerous coasts, or wait for conditions to change. Storms could damage sails and rigging, while calms could leave a ship drifting or stalled. Understanding wind explains why a vessel's location on a map does not tell the whole story of its journey. Routes were shaped by moving air, local knowledge, ship design, and the need to preserve both cargo and crew.