Open the Touchpad module in System Settings and move to the Touchpad information page.
Important
Older versions (before 1.2) of the xf86-input-synaptics touchpad driver do not report touchpad information. If you are using such a driver version, this page will be disabled.

The line right below the name tells you, how many separate fingers are detected by your touchpad during taps. Most touchpads will only detect a single finger, but modern or expensive laptops (e.g. MacBook laptops from Apple Inc.™) will have better touchpads.
The Buttons box tells you, how many buttons your touchpad has. You might notice, that even if your touchpad physically only has mouse button and mouse button, the mouse button is also checked. In this case, you can reach the mouse button by pressing mouse button and mouse button at the same time.