How does Ray.new(Origin, Direction) work?

I noticed something a little peculiar about Ray.new() and I was wondering if anyone knew why.

I wanted to create a ray cast from one cube to another cube, so I simply inputted the Origin and Direction like this:

local rayCast = Ray.new(Cube.Position, targetCube.Position) 

I thought it would be like a CFrame.new(Position, LookAt) type deal, but I found that the ray cast was firing at an angle instead of directly in the direction of the target.

I checked out the API and found this bit of code and applied it to my own ray cast

local rayCast = Ray.new(Cube.Position, (targetCube.Position - Cube.Position).Unit * 300)

Why does this directly target the cube, as opposed to my first attempt where it shot out at an angle?

Thanks.