dependencies are other packages required by the package you are trying to install. linux uses a very modular apparoach to software, and applications rely on others to do their job. as such, you often need to install subordinate tools before the package you want to use is accepted. installation mangers like yum and apt-get resolve these dependencies automatically for you though, so you may want to look at that.
this also has nothing at all to do with networking, please pick your forums more carefully next time