What is "t" in bicubic interpolation?

I was reading about bicublic interpolation on wikipedia. I came across the variable t which is not defined.

The equation is:

Can anyone please tell what this variable means and what are the usual value(s) for it?

t is any number between 0 and 1.

p(0) is the starting point of the curve and p(1) is end for one dimension.

for example by choosing sufficiently small dt you can plot a smooth curve like this

dt = 0.01;
for(var t = 0; t < 1 ; t += dt)
{
   draw( p(t) );
}