Using parametric equations in three space (n- space too if you can envision n dimensions).
The form of a line in three space has the general form
x = a1 + b1*t
y = a2 + b2* t
z = a3 + b3*t
which can be rearranged into another common form for lines in space
(x-a1)/b1=(y-b2)/b2=(z-a3)/b3
Another easy to looks at the geometry, a point in a plane is a intersection of two lines. And a line in a space is an intersection of two planes.
BTW the equation of a line in two dimensions (aka a1*x+b1*y=K) becomes a plane in 3 dimensions.
You might also look at
A line in 3 Dimensions
Rap