The important stuff you need to know about tag sequencing. First the difference between Tag sequencing and tag firing is important. It's essentially about the priority and order that tags will be fired. It uses a JavaScript library to load the web pages all at once. You can configure your tag configuration using advanced settings. The most common time to use tag sequencing is when you want to pull data off a page before firing another.
Key Takeaways:
Tag sequencing is different than tag firing priority because it allows you to specify a particular order for tags to fire.
Tag sequencing is commonly used to extrapolate data from a page that can be used to create custom dimensions using the main tag.
Tag sequencing allows you to set tags to fire before or after an event as well as both before and after.
“The purpose for this feature is to set up your own firing sequence separate from the normal flow of your GTM container to do things such as, dynamically pull data from a page to be used in tag in the same event.”
Read more: https://www.lunametrics.com/blog/2018/02/08/google-tag-manager-tag-sequencing/