Whats the difference between nondenominational and interdenominational and do they have the same beliefs?

In general there is very little difference between the two. A church is considered "nondenominational" if it has no formal connection to a formal denomination; it may belong to a group or "fellowship" of like-minded congregations, but said fellowship is not recognized as a denomination, and rarely does such a fellowship have anything but a rudimentary overseeing government. A church may call itself "interdenominational" if it tries to appeal to people from a variety of different denominational backgrounds. These churches may be nondemoninational as well, or they may belong to a denomination that tries to minimize the differences between denominations, focusing on a base faith, for example, in Christ. Details of belief systems between different nondenominational churches, as well as interdenominational churches and organizations, will vary greatly, depending on the backgrounds and components of the individual congregations.