Effectively there is no difference between these two terms; it just seems to be a case of preference on the part of the manufacturer on a given component.  These electronics almost always do two things:

1) Boost - They increase your overall signal as well as adding some degree of compression.  This gives your notes a more consistent attack that's like a hot knife through butter, even with a clean signal.

2) EQ - Unless you have a multi-band preamp (like those found on acoustic-electric guitars), you more likely find that preamps just boost a single band.  For example, EMG's SPC ("Strat Presence Control") gives a boost around 5 kHz.  Other models modify other bands similarly.

The marketplace is incredibly varied, so there are more and wilder things than the few I have featured here in most of these categories.  Look around the web if you are interested in some particularly experimental devices.

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