Product analytics gives you a one-page view of how your products are selling, drawn from your invoices for a chosen year. Use it to spot your best sellers, see how revenue moves through the year, and check the make-up of your catalogue.
Go to Products → Analytics. Use the year picker in the top corner to choose which year to report on, and the refresh button to reload.
Across the top you'll see four figures: Active products, Unique products sold, Total units sold, and Product revenue for the selected year.
At the bottom, the Revenue by product table breaks revenue and quantity down by product and month, so you can drill into the detail behind the charts.
The figures come from issued invoices, so a brand-new product won't appear until it has been sold. If a year looks empty, check that you've selected the right year and that invoices exist for it.