Every person may learn a different way to play volleyball, but for the most part it's the same concepts but in a slightly different version. The volleyball rules that are changed the most are the ones for recreation.
Volleyball rules for recreation are usually changed a little bit, especially for the younger kids. One reason why the rules are changed is because it's easier for them to learn and to also make it fair. Some of the rules changed for the younger kids in recreation volleyball are the serving line; it's up a little bit and the net is usually lower.
Recreation volleyball is out there so children can learn and have fun without being so competitive. Or even as you get older you can play recreation volleyball just to keep you active on the off season.
However, there are also different rules for different countries sometimes, but if you play for the NCAA, no matter what country you are, all the rules are the same. Probably the most common foreign volleyball rules are the Spanish. These rules originated in Spain in about 1896 and was inspired the German game, Faust Ball. Honestly, I'm not too familiar with the Spanish rules, but only time you would have to worry about them is if you're on a Spanish team which they should explain everything for you.
Volleyball rules, some many different types so you pick the way you want to play. As long as you're having fun don't worry, you'll learn the rules eventually so until then just keep on trying!