understanding some symbols in replace function

[hisoka]

var x = " hello w3schools how are you this is the site url http://w3schools.invisionzone.com"

var y = x.replace (<\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b>/g , '&lt;$1$2&gt;$3&lt;/$1&gt;')

 

could you please tell what do these symbols mean &lt;$1$2&gt;$3&lt;/$1&gt;   ?

 

Edited June 14, 2018 by hisoka

[justsomeguy]

The numbers after a dollar sign are different matches in the pattern.  The rest are part of the replacement text.