Lift (force) contributing factor of ascent
A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and therefore can act in any direction.
If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force.
Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planing lift, in which only the lower portion of the body is immersed in a liquid flow, is used by motorboats, surfboards, windsurfers, sailboats, and water-skis.False explanation based on equal transit-time
The "equal transit time" explanation starts by arguing that the flow over the upper surface is faster than the flow over the lower surface because the path length over the upper surface is longer and must be traversed in equal transit time.  Bernoulli's principle states that under certain conditions increased flow speed is associated with reduced pressure.  It is concluded that the reduced pressure over the upper surface results in upward lift.A serious flaw in the equal transit time explanation is that it does not correctly explain what causes the flow to speed up.  The longer-path-length explanation is simply wrong.  No difference in path length is needed, and even when there is a difference, it is typically much too small to explain the observed speed difference.  This is because the assumption of equal transit time is wrong.  There is no physical principle that requires equal transit time and experimental results show that this assumption is false. In fact, the air moving over the top of an airfoil generating lift moves much faster than the equal transit theory predicts.  The much higher flow speed over the upper surface can be clearly seen in this animated flow visualization.