What does t represent in Bézier curves?

I’ve been looking at roblox wiki to try and understand Bézier curves and I’ve come very close, one thing that I don’t understand is that for the third argument in the function lerp, roblox used t instead of p3, so how does the script know the third part, and what does t represent? Script is below:

function lerp(a, b, c)
    return a + (b - a) * c;
end;

function quadBezier(t, p0, p1, p2)
    local l1 = lerp(p0, p1, t);
    local l2 = lerp(p1, p2, t);
    local quad = lerp(l1, l2, t);
    return quad;
end;