If light only travels straight, how can gravity bend it?

If something is bent, it's no longer straight. Light always travels in a straight line and thus should never bend. Yet observations show that gravity does bend light. Or, more accurately, gravity bends the path of light.

With things like gravitational lensing, we can see how gravity and light interact. 
     Looking at this, it's easy to think that gravity bends light itself. However, in reality, light only appears to be bent: it's really still straight.

     Objects in the foreground block our view of objects in the background. With gravitational lensing, light from the background object is bent around the foreground object. As such, we can see what should otherwise be blocked from view. 

Two otherwise seperate concepts are needed to understand this. 
     One: light always travels the shortest distance possible. That is, it always travels straight. 
     Two: gravity bends spacetime (the fundamental fabric of the universe). That's the foundation of how gravity operates.

Putting these two concepts together results in the explanation.
     If spacetime itself is curved, any straight lines on it appear to be curved. 
     If light moves along this gravity-caused curve in spacetime, the path of the light is still technically straight. 
     Yes, it looks curved, but that's only because space itself is curved.