What is the difference between regulating and
adjusting a watch?

This is simply adjusting the regulator (an adjusting
lever usually with a S slow or F fast range of setting-
images below
) so the watch keeps accurate time in the
position that it is in
at the time of regulation (i.e.dial up
(DU), pendant up (PU)).  A timing machine is use in
order to make adjustments rapidly. This is why the
acronym COR  (Clean, Oil, Regulate) is used as
opposed to COA. Even though the watch has be
regulated, it still will run at different rates in different
positions.  The task in regulation is to adjust it so that
average running rate is as close to a zero error in
the most common positions. Thus, the correct setting for
the regulator will be slightly different for each owner,
depending on how the watch is worn or carried (this is
sometimes referred to
personal error). An owner, if so
inclined, may carefully nudge the regulator with a
toothpick in order to make fine adjustments. Note,
however, that the more accurate regulators are adjusted
by a threaded component, and is more difficult to adjust.
 If in doubt, let an expert adjust the regulator
images below).
(Please see a complete COR checklist)
Contact me or call 530-520-1478
 Adjusting a watch involves procedures that include
ensuring the balance wheel is 'balanced' (poised),
adjusting the hairspring, and even shaping the balance
pivots and adjusting how the hairspring is attached to
the balance wheel.

 The three critical adjustments are for position (as
defined above, see
accuracy), temperature (the ability
to keep good time over a range of different
temperatures), and isochronism (the ability to keep an
even rate over the life of one spring wind, typically 24
hours). An un-adjusted watch should run reasonably
constant in two to three positions (for a pocket watch
dial up, pendant up, pendant left/right) as these are the
most common positions the watch would encounter
either in the pocket, or on a table at night.  High grade
watches are adjusted to five positions or more.

To illustrate the work involved in adjusting a high grade
watch, go to this link:
Fine Adjusting article at Timezone.com
Common Regulator
Fine adjusting regulator (micrometer).  This
one is moved by turning the adjustment screw.
Care must be taken when adjusting this, as it is
easy to slip an scratch the movement, or hit the
balance wheel. If you have any reservation,
contact your watch repair person.