\b and \B are confused

Question

1. Can any master explain it in an easy-to-understand way?

2. What is the difference between putting \B in front and behind

$zz = '/\Bthis/' and $zz = '/this\B/'

Answer 1

/Definition starting point, \b is escape, personal understanding.

Answer 2

Personal understanding

You are talking about regular matching, right?

The former matches xxxthis
The latter matches thisxxx