A chest voice is much deeper and resonating, using the greatest lung capacity and diaphragm to project sound. A head voice is usually thinner and drawn not from deep in the chest but generated mostly form the throat area. Also those nasal, whining boy band voices? Those are head voices.

Head voice and Chest voice are euphamistic terms that refer to two different passagio (or "registers) involved in singing. The chest voice refers to the lowest range of any given person and generally encompasses the speaking range as well. It is so called because you may feel vibrations in your chest when singing in this register (side note, there is no such thing as chest resonance as there's nothing but gooey stuff in your chest and you need hard surfaces to bounce sound around...no, your ribs won't work for this!) Head voice is the upper register, so named because when you sing in this register you feel the vibrations in, you guessed it, your head! And yes, there is head resonance because there are all those lovely hard surfaces in you head for the sound to ping off of. There is also something called the middle register in between the other two. It doesn't get a nickname but its the most important of all because an improperly balanced middle register will really screw up the chest and the head. They all come from the same place-air from your lungs passing through the vocal folds causing them to undulate. One doesn't come from the chest while the other comes from the head (they are really, really misleading terms that cause folks to draw incorrect pedagogical conclusions).

http://ccrma.stanford.edu/CCRMA/Courses/150/singing.html Registers, Voices, and Muscles Voice registers correspond to differences in tone caused by different adjustments of the larynx. Two (``heavy'' and ``light'') or three (``chest'', ``middle'', and ``head'') registers are commonly identified. In the heavy or chest voice, the thyroarytenoid muscles are active and hence shortened. They thicken the vocal folds, which results in their remaining closed over an appreciable part of each cycle of vibration. In the light or head voice, the thyroarytenoid muscles are passive. In this state they offer little resistance to the cricothyroids, which apply substantial longitudinal tension to the vocal folds, lengthening and thinning them. The glottis closes only briefly, or not at all, and the resulting sound has fewer harmonics than the chest voice. The reference to boy bands is my own interpretation.

"Two or three registers are usually recognized in the classically trained voice. These are, in the female voice, the chest voice, middle voice, and head voice and in the male voice, the chest voice, head voice, and falsetto. The term "chest voice" refers to the tonal quality of this register and the sensations felt while singing." The head voice is "The highest register of the voice, as distinct from the lower register (chest voice)." Source: http://www.music.vt.edu/musicdictionary/textc/ChestVoice.html Here are some interesting information from singing lessons: http://singsmart.com/freesingingarticles/elevatortheory.html http://www.vocalrelease.com/h.singing.w.htm