You need to add [301] in htaccess

A query related to friendly url.

I am designing a site from 0 in php and I was wondering if it is necessary to add the [301] in the Rewriterule line as in the following example:

Options +FollowSymLinks
RewriteEngine on
Rewriterule ^rubro/([a-zA-Z0-9_-]+).php rubro.php?id=$1 [301]

If so, in what case is it better to use it?