Analytics Tools
It's important for product managers to be on top of their product's KPIs. Thats why analytics tools such as Google Analytics have become a staple in every product manager's toolkit. These tools offer the ability to look at aggregate data and also dig deep into a single user's journey.
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Google Analytics
The de-facto standard for analysing your site's performance at an aggregate level. Track everything from sessions, to individual events. Create customised reports, of different user segments, split your data by various dimensions to get a deep understand of what's working well and what needs improvement.

Mixpanel
Mixpanel is an event centric analytics tool focused on helps product managers and marketers in understanding the user journey and how best to positively influence conversions and product engagement.

Looker
Now a part of Google Cloud, Looker is a data exploration tool that has rich visualisation capability while being easy to use for the average user. It does require fair upfront investment for setup but is easy to maintain moving forward. Ideally for teams that have resident data analysts or engineers.

Tableau
One of the early products in the BI space, Tableau offers multiple products for various types of use cases. It is a data exploration tool at heart with lots of customisability and creating visually rich reports.