Usability testing is the process of testing any product's functioning with the help of customers. You can ask your customer to spend a few minutes to test the usability of the product.
Product adoption is where the user is acquired, activated, and retained. This is better in long term as it helps improve your product metrics.
Here are the 10 Best Product Analytics Tools that provide you both qualitative & quantitative data on digital products to improve the user interaction and product improvement.