Why we using this "target=_blank"

Answer 1

The target attribute specifies where to open the linked document.
The _blank value opens the linked document in a new window or tab.
https://www.w3schools.com/TAgs/att_a_target.asp

So we use this if we want the document to open in a new window or tab.

Answer 2

To open the link in new tab or window. There are other options like target="_parent" , target="_self" ...etc. target="_blank" just opens the link in new tab thats all.
For more info:
https://www.w3schools.com/tags/att_a_target.asp

Answer 3

To open the link in a new tab