Core Tools

Your controllers can have different tools attached to them as you need such as the Grabber, Navigator, Sketcher or Destroyer. Each controller can (and typically will) have different tools.
The primary tool on your main hand is the Grabber, and the Navigator on your off hand.
Press and hold the Menu button (A button on Index & Oculus) to summon the Tool Wheel Menu which lets you change tools. Twist your hand to select the tool you want and release.
For quick access, you can click the Menu Button to toggle between the current tool and the primary tool (Grabber on your main hand, Navigator on your off hand).

Tool Status

Just above and outside of your controller is a small square status panel for the current tool. This will usually show you the current tool selected and additional status info. Many tools such as the Grabber will show you info about what it's pointing at such as the thing's name.