The Pinterst Tag is a small script that when placed on your website that allows you to target website vistors with Pinterst ads based on their behavior.
For example, lets say someone visited your ecommerce store and scrolled through the shoes category and eventually added a pair of stilettos to the cart but did not check out. That user definitely was close to purchasing and has a high degree of intent.
With the Pinterst Tag on your site you can target visitors exactly like him/her with an ad next time they are scrolling on Pinterest.
Watch for duplication in tracking code and test that the tag is only firing once and not multiple times on a single page. If it is that will cause data within Pinterest to be inacurate. Expecially event data.
For example, if a order placed event is fired twice then the cost per acquisition and return on ad spend Pinterst displays could be off by 2x.
Typically we suggest always implementing tags via a tag manager of some kind both Segment and Google Tag Manager are good options.