Explanation
GTL (Guide Template Language) is a scripting language that allows parsing and displaying JSON or XML data within an email. GTL can be used to make API calls to external services, such as the Sunny Sky API, and display the response within the email. For example, NTO can use the HTTPGet() AMPscript function to retrieve the weather information from the Sunny Sky API as a JSON object, and then use the TreatAsContent() AMPscript function to parse and display the JSON object using GTL tags and variables. References:
https://help.salesforce.com/articleView?id=sf.mc_es_guide_template_language.htm&type=5
https://help.salesforce.com/articleView?id=sf.mc_es_httpget_ampscript_function.htm&type=5https://help.salesfo