There are 4 possible screens in this GPS tracking window:
With a plugged in GPS receiver (has to be supported by your operating system) a simple click on [Connect] connects the GPS to QGIS. A second click (now on [Disconnect]) disconnects the GPS-receiver from your computer. For GNU/Linux gpsd support is integrated to support connection to most GPS receivers. Therefore you first have to configure gpsd properly to connect QGIS to it.
If you want to record your position to the canvas you have to create a new vector layer first and switch it to editable status to be able to record your track.
Figure GPS Position:
Figure GPS Strength:
Figure GPS polar window:
A click on [Connect] again initiates the connection to the GPS receiver.
Figure GPS Tracking 2:
Activating Map centering allows to decide in which way the canvas will be updated. This includes ‘always’, ‘when leaving’ if your recorded coordinates start either to move out of canvas or ‘never’ to keep map extent.