As Christi says, "unvoiced" doesn't mean silent. It means that you make the sound by pushing air through your mouth, without using your vocal chords. (You use your vocal chords to make vowel sounds and "voiced" consonant sounds.)
For example, the sound "g" is voiced, but "k" is unvoiced. You make the two sounds with the same part of the mouth, but when you say "g" you use your vocal chords, and when you say "k," you only use a puff of air.
The sounds "b" and "p" are also very similar, but "b" is voiced, and "p" is unvoiced. The sound "d" is voiced, but "t" is unvoiced. The sound "v" is voiced, but "f" is unvoiced. The sound "z" is voiced, but "s" is unvoiced. Try making these pairs of sounds, and you may be able to understand the idea of "voiced" and "unvoiced" more easily.