jQuery easing function — variables' comprehension

Question

How does the easing function for jQuery work? Take for example:

easeInQuad = function (x, t, b, c, d) {
    return c*(t/=d)*t + b;
};

How d

Answer 1

Looked through the 1.11 jquery code. The x parameter seems to mean 'percent', independent from initial time value. So, x is always (0 <= x <= 1) (means abstract coefficient), and t is x * d (means time elapsed).