Question: I have heard that when a sailboat is sailing against the wind, it operates on the principle of 'lift'. I am unable to understand the explanation, based on Bernoulli principle, completely. My question is, when it says 'lift', it literally means that the boat is being 'lifted' out of the water? Like when we throw a stone across the lake and it skims and hops on the water?

Answer: 
An important point that is often overlooked is that sails do not just generate 'lift', but generate lift in a direction. The pressure differential across the sail's surface is typically much larger near the leading edge, which results in more forward force than you might expect. The two sails (with a sloop) also interact in a way that generates more forward force.

You can see some simulations with different sail configurations, and comparison to the performance of a real sailboat at this site:

<https://sites.google.com/site/sailcfd/>
Well, [according to this](https://physics.stackexchange.com/a/295/85020) Bernoulli effect is NOT the cause of lift.

> 
> Basically planes fly because they push enough air downwards and receive an upwards lift thanks to Newton's third law.
> 
> 
> 

It is clear that blowing over a piece of paper pulls it up ([video](https://youtu.be/025lsG3VHKM?t=74)).
Here: fast air => lower pressure => paper pulled up. Right.

But that IS NOT the case for sails and wings. Wind arriving to a sail/wing goes ALL of it at the SAME speed. The air above the wing / on leeward of a sail does not spontaneously accelerate up. It gets speeded up by a a lower pressure in that zone. Thus, the "fast air" is not the cause but THE CONSEQUENCE.

What does it cause the low pressure zone above a wing / on leeward of a wing?

What is for sure is that wings/sails deflect air. Then for wings and sails:

Main cause: air deflection => change of pressure => changes in air speed.

That's it.

Don't get confused by the fact that Bernoulli equation can be effectively used to measure lift. It's perfectly right to estimate the real cause (air deflected downwards) by a direct effect (change of pressure).