Jewish men wearing their hair in this way is a symbol of their belief. It is common to see a Jewish man with short hair apart from two long bits at the side which they have curled into tight ringlets, that they wear down their sides. Often they will wear a hat and have an untrimmed beard as well.
Not all Jewish men wear their hair like this, the type you are reffering to are called 'Hasidic Jews'.
Jewish people follow a script called a Torah, which gives them instructions on their way of life. They believe that all of the teachings that can be found in the Torah were given to them by God, through Moses.
One of the teachings that can be found in the Torah is about the way that Jewish men wear their hair. It states that they must not cut the hair of their peyos. The term peyos meaning any hair that is in front of the ears.
They are however, still allowed to trim their sideburns with scissors, but many men will grow these bits of hair long and in ringlets to show that they are following the Torah tightly and emphasise their religion.
As far as I know curling the sideburns into ringlets is just a matter of taste, as not all men will wear them in this way.