Connected to the base is the first bit of the arm which can pivot up and down on the base. Connected to that is a hand which can move in and out. I will start off by explaining how to manage serial-link structures. The basic structure of this system is a series of objects of some length linked together by hinges. The hinges can pivot in the x, y or z-axis.
Lets first look at the robot arm example.
This is a serial linked structure. Here, the names of parts of the robot are enclosed in colons, and the names of pivots are enclosed in brackets. The names of the pivots describe how they can move. An x-axis pivot can rotate in the y,z plane. A telescopic joint can change length, rather like a telescope unsurprisingly.