In the program options you can establish if you want it to automatically recognize the language and translate it to your own (there are more than fifty to choose from), or if you prefer it to translate only from one specific language.
Of course, you can also use the program as though it were a traditional translator, and simply write text to translate in its text box or copy a fragment from a different program. The translation won't take more than a few seconds to appear.
Linguarde is a useful tool, but keep in mind that you need to be connected to the Internet in order to use it. If you can do that, then you'll have a discreet, effective translator.