Hi @SoCoolCarter, welcome to the community. 

So generally speaking, an email template can be customized by any of these variables:

• Event variables (variables or values that were part of the event). 
• Profile Properties (values that are part of the Profile including custom profile properties)
• Catalog based values (if you have a specific product ID, you can expand it to include values from the product catalog).

These three baskets of data gives you virtually unlimited options of data to include in an email template, it’s only constrained based on the data that is passed to Klaviyo.  In some cases, third party apps (such as a Review Platform with product reviews) that integrate with Klaviyo will add additional data (profile data, or event data).  In other cases, data can come from custom integrations via Klaviyo’s API or even data you uploaded or data you collect from Signup Forms.  

In some cases, you may requires some template logic or coding.  In other scenarios, you may simply have to just include the correct variables that are available. Here’s a good guide on how to use these values/variables in a template:

• How to insert template tags and variables into text blocks (new editor)

I recommend you see what data you have available and then work your way up to what you would *like* to see and ask follow-up questions here on how to go about including it.  In many cases, the data is already there ready for you to use, but this is dependent on which apps, platforms, and data you already have.  If you haven’t picked specific apps, working with apps that already integrate with Klaviyo can fast track the available data problem.  You can see the whole catalog of apps that Klaviyo already integrates with in the Integration Directory:

• https://connect.klaviyo.com/integrations

Hope this helps!