Yes, nylon strings can be used in guitars. Some guitar manufacturers produce guitars nylon strings so you can actually buy a guitar pre-stringed with nylon. Many people choose to play guitars with nylon strings because they are not that hurtful to the fingertips as compared to steel strings. This is great for people who are wanting to learn to play this string instrument for the first time.
Nylon stringed guitars are also chosen by people who love classical and folks music. Nylon strings produce mellow and soft sounds that are perfect for these types of genre. You may need to tune it every time you are going to use at more likely to loosen.