You should check the glossary at the end of the book.
Besides, check this out (page 118):
H I G H/LOW 1 , 2 , 3 , AND 4
A reliable sign that a pullback in a bull or in a trading range has ended
is when the current bar's high extends at least one tick above the high
of the prior bar. This leads to a useful concept of counting the number
of attempts that this occurs. In a sideways or downward move in a bull
trend or a trading range, the first bar whose high is above the high of the
prior bar is a High 1, and this ends the first leg of the sideways or down
move, although this leg may become a small leg in a larger pullback. If the
market does not turn into a bull swing and instead continues sideways or
down, label the next occurrence of a bar with a high above the high of the
prior bar as a High 2, ending the second leg. There needs to be at least a
tiny trendline break between the High 1 and the High 2 to indicate that the
trend traders are still active. Without this, do not yet look to buy since the
High 1 and High 2 are more likely to be just part of the same first leg down.
In a strong upswing, the High 2 entry can be higher than that of the High
1, and in a strong downswing a Low 2 entry can be lower than that of the
Low 1. Some pullbacks can continue to form a High 3 or a High 4. Beyond
a High 4, it is likely that the market is no longer pulling back in a bull move
and instead is in a bear swing. Wait for more price action to unfold before
placing a trade.
Best regards
Juan Pablo Balboa
Argentina
