Time Dilation Graph: Variables & Lorentz Contraction

[nicekarmajobs]

Can anyone tell me what exactly do the variables "Time Dilation" and "Velocity of a fraction of the speed of light" represent (in this graph) from the lorentz contraction?

http://www.fourmilab.ch/cship/figures/gr_timedial.gif

Does the x-axis represent "v/c" or is it "v^2/c^2"? What does the y-axis represent? Which "t"? Or is it one "t" over another?

 

[kuruman]

Both axes represent dimensionless quantities. The x-axis is v/c, what some textbooks call β. The y-axis is, as you say, "one t over another". More simply, it is the relativistic factor

$$\gamma=\frac{1}{\sqrt{1-v^2/c^2}}$$

I guess what you are supposed to take home from this graph is that when v/c is greater than 0.95 or so, the time dilation factor starts getting really noticeable.