Change in boiling point of water
Boiling point of a liquid is defined as the temperature at which the pressure inside the liquid has reached equilibrium with the atmospheric pressure and the liquid does not get any hotter. Of course, in our daily life, this temperature is 100 degrees Celcius and we often just cram this into the head and forget about the definition of boiling point.
Now, let's approach this concept from a different perspective so boiling point doesn't just sound like boiling "hot". Suppose we clime up on Mount Everest where the air is thin, a.k.a. atmospheric pressure is low, obviously it takes less temperature for water to reach its boiling point because pressure is directly related to the temperature (or let's say how fast molecules move around). For those interested in mountain climbing, it should not be a surprise that you cannot make good tea with the water you boil on top of a high mountain.
Now, let's go into the kitchen where our mothers (sometimes fathers) prepare us delicious meals that we always take for granted. Pressure cooker is always a handy tool to have if we want to boil huge chunks of meat till it becomes easy to chew. The way it works is that pressure cooker seals the vapor as the liquid heats up but there is a valve that allows some vapor to go out so pressure won't keeping going up. By having a high pressure inside the tightly sealed pot, the liquid's boiling point can be well above 100 degrees and that's really helpful in breaking down the tight fibers in huge chunks of chewy beef.
Finally, astronauts are also concerned about this part of physics because if they have a leaky space shuttle that keeps loosing pressure as it ascends. Eventually, the pressure will come down to a point where the boiling point of water is around 37 degrees (normal body temperature). You can imagine the catastrophe ensuing since human body is mostly composed of water. In fact, there were several Soviet cosmonauts who perished in an accident of pressure loss in space shuttle.