Men and boys commonly wear both shorts and swim trunks. What is the difference between the two? In what situations do they wear each one?
The history of both shorts and swim trunks is similar. Both have gone back and forth between being ultra short, short, longer and long over time. In recent history we have seen a phenomenon called "board shorts," which are traditionally long.
Shorts are primarily worn during social situations that occur outside the water. Shorts can be worn to pretty much any kind of informal event or during any kind of activity except for work. Unlike shorts, which are multifunctional, swim trunks are pretty much worn in and around the water. They are made to be used to swim and lounge around water.
The features of shorts and swim trunks are what differentiate them. Shorts are normally made of some kind of cotton. They come in all different colors, patterns and sizes. Swim trunks have mesh inside and are made of a waterproof material that will dry very quickly once you have left the water. Regular cotton shorts will take much longer to dry.
Where you live makes a big difference in how often you wear shorts and swim trunks. If you live in a tropical place, where it is warm for much of the year, shorts and swim trunks will both be worn a lot more often than in a place where it is cold during certain seasons.
The main consideration when buying shorts or swim trunks is the amount of time you're going to spend swimming. If you're going to be outside in the hot sun a lot but not be in the water, regular shorts are the way to go. If, however, you're going to be in the water a lot but also plan to be socializing and spending time out of the water, swim trunks would be a smarter buy.