Dikt is a dictionary that implements the client side of Dict protocol. Dikt is a network application, it looks up words on dict servers. You don't need to install any dictionaries, you only need a connection to Internet. You can find information about Dict protocol at Dict web site.
Dikt is very similar to web browsers (here is a screenshot), and it should be equally easy to use. It has the advantage over web browsers that is much smaller and faster. Web dictionaries are good for off searches, but when you need to work with a dictionary, you will want a dedicated application.