Manual

Quest Experience
When you turn in a completed quest, you gain an experience reward. This
quest reward is often substantial, and equal to several, if not a dozen,
monster kills at once. Quests will range in difficulty, so the rewards will also
vary.
Doing quests is an extremely efficient way to earn experience and gain
levels. Players who only kill monsters do not typically level as quickly as
those who also complete quests. Furthermore, not only do quests help you
level more quickly, but they also carry material rewards as well.
The Experience Bar
Stretching across the bottom of your screen is your experience bar. At the
beginning of a level, it is empty, but as you earn experience, it begins to
fill. You can mouse over the experience bar to see your current experience,
and the amount you need for next level. When it fills up completely, you
gain a new level, and the experience bar resets to zero.
In addition, the amount of experience you need for the next level increases
an incremental amount. Leveling up becomes progressively harder, not
only because your challenges are greater at higher levels, but also because
the experience requirement grows.
Rest State
In World of Warcraft, the rest
state has a great effect on how
much experience you earn
from kills. When your character
is rested, they earn 200
percent of the experience from
a kill. However, rest state is a
temporary condition, and you
become less rested after you accumulate a certain amount of experience
through encounters.
52