Is there an equivalent of Synaptic (graphical UI) for Fedora?

By default, Fedora 20 installs gnome-software for this purpose. Not sure if this is exactly what you are looking for. It is a GUI for managing and installing packages, but looks more like (or better say, wishes to look like...) MacOSX appstore. This may or may not be of your taste, but allows you to browse installed and uninstalled packages as well as identifies the currently available updates for the installed ones.

Edit: gnome-software is Application oriented (and not package oriented), thus it may not show individual packages for webservers, libraries, etc.

Apper, in the other hand, does. To install Apper, just run yum install apper as root in a terminal.