Long story short, yes they are. Nylon guitar strings are referred to as having high or low tension, with high-tension strings offering a heavier feel and low tension an easier-to-play feel. Even ‘high’ tension strings have less tension than a steel or bronze set - and it’s one of the main reasons why so many people start on a nylon string classical guitar.
In a set of classical strings, the top three strings are made from clear or rectified nylon, with the bottom three typically using bronze or silver-plated copper wire wrapped around a multi-filament core. You’ll only need nylon (sometimes known as ‘classical’) strings if you’ve got a classical guitar - and it’s important that you don’t get mixed up between nylon and steel strings. The difference in string tension means that if you put steel strings on a classical guitar, you run the risk of seriously damaging your instrument.