First of all, if you don't know what dependencies are, you are obviously a Linux newbie. There is absolutely nothing wrong with that. No one is born with an innate knowledge of Linux, so everyone is a newb at one time. However, I would not recommend ANY test release of Fedora Core for a newbie. The test releases are intended for experienced testers, which also leaves me out. IMHO at this point you would be far better served with Fedora Core 3.
Anyway, back to your question. When you try to install a package, and you get Failed dependencies, it means that the package you are trying to install uses code from other packages. In this case, fvwm needs sections of code from libreadline and libstroke. Instead of reinventing the wheel all the time, programmers often reuse chunks of code that performs a frequently used function. These chunks of code that do common tasks are often collected in a library. Just as books are collected in a library. So, if you need information on a particular subject, instead of starting from scratch researching said subject, you can go to the library and see if someone else has already done the research and written a book on it. If so, it saves you a lot of time and work. Same when writing programs. If you need to send info to the screen, or get info from the keyboard, instead of writing this code yourself, use code that someone else wrote and has been put in a library.
Almost every package that starts with the three letters "lib" is a library. fvwm uses functions contained in libraries libreadline and libstroke. What you ran into is referred to as "Dependency Hell". The more complex the application, the more chance you have of "Dependency Hell".
One way to avoid dependency problems is to use yum to install packages. Yum checks for dependencies and automatically downloads and installs all dependencies for the package you are trying to install. http://www.fedorafaq.org/
describes how to set up yum in Fedora Core 3.