If the vocal chords vibrate during the entire occlusion time of a consonant, the consonant is
"fully voiced". If they vibrate during only a part of the consonant occlusion time, the consonant is
"partially voiced". If they do not vibrate during the consonant occlusion, but start vibrating immediately after the consonant release (when a consonant is followed by a vowel), it is a
"tenuis voiceless consonant". If they do not vibrate during the consonant occlusion, and do not start vibrating immediately after its release, but there is a noticeable delay between a consonant and a subsequent vowel, it is an
"aspirated voiceless consonant". There can also be different degrees of partial voicing, as well as different degrees of aspiration.
Wikipedia provides more details on this phenomenon:
Voice onset time - Wikipedia, the free encyclopedia.