As you can see, the default excerpt length is still 150, but we’ve also applied
some filters to it. A filter allows you to write a function that modifies the
value of something — in this case, the excerpt’s length. The name (or tag) of
this filter is excerpt_length, and if no functions are attached to it, then its
value will remain 150. Let’s see how we can now use this to modify the
default value.