Google Analytics is a tool that helps website owners understand how people use their websites. There are two versions: Universal Analytics (UA) and Google Analytics 4 (GA4).

Data Models:

● UA: UA groups user actions into sessions, like a group of activities during a visit to a website.

● GA4: GA4 focuses on tracking individual actions, like when someone clicks a button or views a page.

Tracking Mechanisms:

● UA: UA uses a special code added to each website page to track user actions.

● GA4: GA4 uses a different code called gtag.js added to each page to track user actions.

Using both UA and GA4 at the same time involves these steps:

Create UA and GA4 properties: 

Set up both versions in separate Google Analytics accounts.

Add the tracking codes:

● UA: Put the UA tracking code on each website page.

● GA4: Put the GA4 tracking code on each website page.

Enable cross-domain tracking (if needed): 

If the website spans multiple domains, enable special settings to track users across domains.

Analyze and compare data: 

Access the analytics interfaces for UA and GA4 to see how people are using the website. Remember to consider the differences in how data is grouped and reported in each version.