Phono Preamps, help

I don't mean to sound stupid, but what is the difference between a phono preamp, a Phono Head amp, and a pre-preamplifier? Are each of these meant to plug into the back of your existing preamp, and if so, how do they differ?
A phono pre-amp (external) or phono stage (internal) takes the very low level signal of a phono cartridge and does two things: it modifies it to correct for RIAA equalization applied during production of the LP (essentially a type of tone control meant to compensate for limitations of the LP technology) AND it boosts the signal to live level (like the output from a tape deck, tuner, CD, or DVD; 1-3 volts typically) which can then be used as an input to a line stage pre-amp. There are also devices (external or internal) that boost the very low signal from a moving coil cartridge (MC) (in the fractions of a millivolt) to a level that a phono pre-amp can handle (these were originally designed for the much higher signal from a moving magnet (MM)cartridge). These are sometimes called pre-preamps or MC amps. They do not compensate for the RIAA equalization, nor do they boost the signal to line level. A phono stage is required for that. However, some phono pre-amps and phono stages have high enough gain or an extra circuit to handle both MC and MM cartridges.
Thanks for the response. Can you answer one more question for me please? If you listen to the phono sections in different preamps, each will have it's own sound. If you add a head amp, or pre-preamp to boost the signal in a phono stage that is not capable of handling a low output MC cartridge, will the sound only be amplified or will it take on the sound characteristics of the Head amp (assuming that the head amp is a different brand than the preamp).
Your sound is of course affected by the sonic & noise charactaristics of every gain stage, cable & connector that it passes through, including a pre-pre. Just ensure that the pre-pre has a flat response (not RIAA equalized) or you'll be equalizing twice as the signal passes through the MM phone stage. Double Eq. is not at all desirable - I can't imagine how bad that would sound!
As to your question about the sound thru different combos of Head amps/pre-pre and pre amps, Bob is correct, every connector and gain stage (gain stage = amplifier)affects the sound. If you have a good head amp, and try it w/ two different pre-amps, you should hear the difference between the pre-amps only. Remeber that there are two common ways to accomplish the RIAA EQ, 1st is active-EQ where the eq is dependant upon the specific gain of the amplifiing stage - when the gain od the device dips, the eq is changed. 2nd passive EQ, where the EQ circuit is independant of the gain stage and will NOT drift as the gain device changes. this is especially significant in tube phono stages. Some tube vendors can offer tubes with specific gain numbers for tubes going into active-eq phono stages.
Happy listening!