Please no hate for lack of knowledge:
I am somewhat fascinated with the subject of black holes. However, I do not understand a concept which is constantly attributed with black holes: that a black hole can attract light and therefore light cannot escape it. What I don't understand is, how? Gravity, as far as I understand, only attracts matter. However, light has no mass (right?), so how can a black hole attract light?
You misunderstand. All objects have some escape velocity, which is the velocity needed for anything (photons or matter) to escape from that object's gravitational field. And that's not the velocity it needs to maintain under some sort of constant thrust, but the initial velocity it needs to, shall we say, coast away from the object. For a black hole that escape velocity is greater than the speed of light.
You might be thinking, "But photons don't have mass." In fact, your original question says that. Perhaps you've heard of gravitational lensing in which a very massive object can bend the light from an object beyond it. Yes, gravity can bend light. While photons have no rest mass, they do acquire relativistic mass at the speed of light and therefore, respond to gravity.
Look at the paragraph "gravity and the photon" in this link:
In the relativistic framework, i.e. large velocities, any energy is also a relativistic mass:
For the photon this means the following equation:
m is the relativistic mass of a photon with energy h*nu.
Gravity attracts relativistic mass, and the photon has one. Read the link further to acquire some intuition.
