TremorSense is an earthbeding move that is similar to the firebending move Illumination. It is very simple. All you have to do is this:

Type in '/bending bind TremorSense'

To activate and deactivate it, all you have to do is crouch. Once you do this, one block of glowstone should appear on the ground below you. The glowstone will not appear unless it is dark so it is only usefull in caves or when it is nighttime.